[PHPC-2647] Out-of-source build: Don't necessarily generate flies in the source tree

[vector-of-bool]

This changeset modifies an AC_CONFIG_FILES directive to configure some of mongoc's files using relative paths. IIUC, using relative paths (instead of absolute ones) will make it read the file relative to the configure script, but write the file with the same name relative to the $PWD of the configure execution. This allows the configure script to leave the source tree more pristine.

To support this, the directories that are (possibly) generated by AC_CONFIG_FILES needs to be added as #include search paths. (The search directories are added based on $PWD, which feels somewhat brittle (is there a better autotools/autoconf variable to be used here? I couldn't seem to make it work otherwise.).)

(I'm not sure if there is an existing relevant Jira ticket for out-of-source build support tasks, so I created PHPC-2647 for this.)

[Copilot]

Pull request overview

This PR modifies the autoconf configuration to support out-of-source builds by changing how generated files are created. Instead of using absolute paths that write files into the source tree, it uses relative paths that write to the build directory.

Changes:

• Changed AC_CONFIG_FILES to use relative paths instead of absolute paths based on ${ac_config_dir}
• Added build directories as include paths using $PWD to ensure generated headers can be found

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[alcaeus]

Note: rebased to resolve conflicts.

I tested this by running phpize in the extension folder, then switching into scripts and running ../configure. Afterwards, I saw an src folder with the expected header files generated. From the scripts folder, I ran make -f ../Makefile, and was greeted by an error message:

make -f ../Makefile
/bin/sh /Users/alcaeus/Code/mongodb/mongo-php-driver/libtool --tag=CC --mode=compile cc -Isrc/libmongoc/src/common/src/ -I/Users/alcaeus/Code/mongodb/mongo-php-driver/src/libmongoc/src/common/src/ -I/opt/homebrew/Cellar/php@8.4/8.4.15/include/php -I/opt/homebrew/Cellar/php@8.4/8.4.15/include/php/main -I/opt/homebrew/Cellar/php@8.4/8.4.15/include/php/TSRM -I/opt/homebrew/Cellar/php@8.4/8.4.15/include/php/Zend -I/opt/homebrew/Cellar/php@8.4/8.4.15/include/php/ext -I/opt/homebrew/Cellar/php@8.4/8.4.15/include/php/ext/date/lib -I/Users/alcaeus/Code/mongodb/mongo-php-driver/src/libmongoc/src/common/src/ -I/Users/alcaeus/Code/mongodb/mongo-php-driver/src/libmongoc/src/uthash/ -I/Users/alcaeus/Code/mongodb/mongo-php-driver/src/libmongoc/src/libbson/src/ -I/Users/alcaeus/Code/mongodb/mongo-php-driver/src/libmongoc/src/libbson/src/jsonsl/ -I/Users/alcaeus/Code/mongodb/mongo-php-driver/src/libmongoc/src/libmongoc/src/ -I/Users/alcaeus/Code/mongodb/mongo-php-driver/src/libmongoc/src/utf8proc-2.8.0/ -I/Users/alcaeus/Code/mongodb/mongo-php-driver/src/libmongocrypt/src/ -I/Users/alcaeus/Code/mongodb/mongo-php-driver/src/libmongocrypt/kms-message/src/ -I/Users/alcaeus/Code/mongodb/mongo-php-driver/src/libmongocrypt-compat/ -I/Users/alcaeus/Code/mongodb/mongo-php-driver/src/ -I/Users/alcaeus/Code/mongodb/mongo-php-driver/src/BSON/ -I/Users/alcaeus/Code/mongodb/mongo-php-driver/src/MongoDB/ -I/Users/alcaeus/Code/mongodb/mongo-php-driver/src/MongoDB/Exception/ -I/Users/alcaeus/Code/mongodb/mongo-php-driver/src/MongoDB/Monitoring/ -I/Users/alcaeus/Code/mongodb/mongo-php-driver/src/contrib/  -DHAVE_CONFIG_H  -I/opt/homebrew/include -D_GNU_SOURCE   -g -O0 -Wall -DBSON_COMPILATION -DMONGOC_COMPILATION -D_XOPEN_SOURCE=700 -D_BSD_SOURCE -D_DEFAULT_SOURCE -D_DARWIN_C_SOURCE -pthread  -I/opt/homebrew/opt/zstd/include -I/opt/homebrew/Cellar/openssl@3/3.6.0/include -DKMS_MESSAGE_ENABLE_CRYPTO=1 -DKMS_MESSAGE_ENABLE_CRYPTO_LIBCRYPTO=1 -DKMS_MESSAGE_LITTLE_ENDIAN=1 -pthread -c /Users/alcaeus/Code/mongodb/mongo-php-driver/src/libmongoc/src/common/src/common-atomic.c -o src/libmongoc/src/common/src/common-atomic.lo  -MMD -MF src/libmongoc/src/common/src/common-atomic.dep -MT src/libmongoc/src/common/src/common-atomic.lo
mkdir src/libmongoc/src/common/src/.libs
 cc -Isrc/libmongoc/src/common/src/ -I/Users/alcaeus/Code/mongodb/mongo-php-driver/src/libmongoc/src/common/src/ -I/opt/homebrew/Cellar/php@8.4/8.4.15/include/php -I/opt/homebrew/Cellar/php@8.4/8.4.15/include/php/main -I/opt/homebrew/Cellar/php@8.4/8.4.15/include/php/TSRM -I/opt/homebrew/Cellar/php@8.4/8.4.15/include/php/Zend -I/opt/homebrew/Cellar/php@8.4/8.4.15/include/php/ext -I/opt/homebrew/Cellar/php@8.4/8.4.15/include/php/ext/date/lib -I/Users/alcaeus/Code/mongodb/mongo-php-driver/src/libmongoc/src/common/src/ -I/Users/alcaeus/Code/mongodb/mongo-php-driver/src/libmongoc/src/uthash/ -I/Users/alcaeus/Code/mongodb/mongo-php-driver/src/libmongoc/src/libbson/src/ -I/Users/alcaeus/Code/mongodb/mongo-php-driver/src/libmongoc/src/libbson/src/jsonsl/ -I/Users/alcaeus/Code/mongodb/mongo-php-driver/src/libmongoc/src/libmongoc/src/ -I/Users/alcaeus/Code/mongodb/mongo-php-driver/src/libmongoc/src/utf8proc-2.8.0/ -I/Users/alcaeus/Code/mongodb/mongo-php-driver/src/libmongocrypt/src/ -I/Users/alcaeus/Code/mongodb/mongo-php-driver/src/libmongocrypt/kms-message/src/ -I/Users/alcaeus/Code/mongodb/mongo-php-driver/src/libmongocrypt-compat/ -I/Users/alcaeus/Code/mongodb/mongo-php-driver/src/ -I/Users/alcaeus/Code/mongodb/mongo-php-driver/src/BSON/ -I/Users/alcaeus/Code/mongodb/mongo-php-driver/src/MongoDB/ -I/Users/alcaeus/Code/mongodb/mongo-php-driver/src/MongoDB/Exception/ -I/Users/alcaeus/Code/mongodb/mongo-php-driver/src/MongoDB/Monitoring/ -I/Users/alcaeus/Code/mongodb/mongo-php-driver/src/contrib/ -DHAVE_CONFIG_H -I/opt/homebrew/include -D_GNU_SOURCE -g -O0 -Wall -DBSON_COMPILATION -DMONGOC_COMPILATION -D_XOPEN_SOURCE=700 -D_BSD_SOURCE -D_DEFAULT_SOURCE -D_DARWIN_C_SOURCE -pthread -I/opt/homebrew/opt/zstd/include -I/opt/homebrew/Cellar/openssl@3/3.6.0/include -DKMS_MESSAGE_ENABLE_CRYPTO=1 -DKMS_MESSAGE_ENABLE_CRYPTO_LIBCRYPTO=1 -DKMS_MESSAGE_LITTLE_ENDIAN=1 -pthread -c /Users/alcaeus/Code/mongodb/mongo-php-driver/src/libmongoc/src/common/src/common-atomic.c -MMD -MF src/libmongoc/src/common/src/common-atomic.dep -MT src/libmongoc/src/common/src/common-atomic.lo  -fno-common -DPIC -o src/libmongoc/src/common/src/.libs/common-atomic.o
In file included from /Users/alcaeus/Code/mongodb/mongo-php-driver/src/libmongoc/src/common/src/common-atomic.c:18:
In file included from /Users/alcaeus/Code/mongodb/mongo-php-driver/src/libmongoc/src/common/src/common-atomic-private.h:24:
In file included from /Users/alcaeus/Code/mongodb/mongo-php-driver/src/libmongoc/src/libbson/src/bson/bson.h:23:
In file included from /Users/alcaeus/Code/mongodb/mongo-php-driver/src/libmongoc/src/libbson/src/bson/bson-bcon.h:27:
In file included from /Users/alcaeus/Code/mongodb/mongo-php-driver/src/libmongoc/src/libbson/src/bson/bson-types.h:23:
In file included from /Users/alcaeus/Code/mongodb/mongo-php-driver/src/libmongoc/src/libbson/src/bson/bson-endian.h:23:
/Users/alcaeus/Code/mongodb/mongo-php-driver/src/libmongoc/src/libbson/src/bson/compat.h:31:10: fatal error: 'bson/config.h' file not found
   31 | #include <bson/config.h> // IWYU pragma: export
      |          ^~~~~~~~~~~~~~~
1 error generated.                                                                                                                                                                                                                                                                                                          
make: *** [src/libmongoc/src/common/src/common-atomic.lo] Error 1

This leads me to believe that we'd need to add additional directories (e.g. src/libmongoc/src/libbson/src/bson) to the includes. Do you foresee this being a typical use case? I'm not sure it's worth the hassle, considering most installs of the extension will be run through pear/pie, where the installer runs configure and make from the temporary folder it extracts sources to, before then cleaning up those sources.