Fix inlining demo after Fuchsia toolchain updates

[boomanaiden154]

Fuchsia recently updated their toolchain to include llvm-debuginfod which needs an additional dependency, cpp-httplib in order to build LLVM properly. This patch adds instructions on how to build this dependency so that the demo still works.

[boomanaiden154]

Waiting on yhirose/cpp-httplib#1580.

As far as I can tell since llvm-debuginfod has been added to the toolchain in the stage 2 CMake cache, it's hard to just disable it in the CMake invocation without doing something slightly hacky that would probably be more prone to breaking things.

[boomanaiden154]

@mtrofin @petrhosek Do one of you mind giving this a review? The mentioned prerequisite patch has landed now.

[boomanaiden154]

Nevermind. Looks like this might still need some more work. Currently failing on building the riscv64 runtimes as CMake claims lld is unable to find the necessary libraries, but the paths seem to be setup correctly.

[35/135] Performing configure step for 'runtimes-riscv64-unknown-fuchsia'
Not searching for unused variables given on the command line.
-- Could NOT find ZLIB (missing: ZLIB_LIBRARY ZLIB_INCLUDE_DIR) 
-- Could NOT find ZLIB (missing: ZLIB_LIBRARY ZLIB_INCLUDE_DIR) 
CMake Error at /llvm-project/llvm/cmake/modules/HandleLLVMOptions.cmake:330 (message):
  Host compiler does not support '-fuse-ld=lld'
Call Stack (most recent call first):
  CMakeLists.txt:156 (include)


-- Configuring incomplete, errors occurred!
See also "/llvm-build/runtimes/runtimes-riscv64-unknown-fuchsia-bins/CMakeFiles/CMakeOutput.log".
See also "/llvm-build/runtimes/runtimes-riscv64-unknown-fuchsia-bins/CMakeFiles/CMakeError.log".
FAILED: runtimes/runtimes-riscv64-unknown-fuchsia-stamps/runtimes-riscv64-unknown-fuchsia-configure /llvm-build/runtimes/runtimes-riscv64-unknown-fuchsia-stamps/runtimes-riscv64-unknown-fuchsia-configure 
cd /llvm-build/runtimes/runtimes-riscv64-unknown-fuchsia-bins && /usr/bin/cmake --no-warn-unused-cli -DCMAKE_C_COMPILER=/llvm-build/./bin/clang -DCMAKE_CXX_COMPILER=/llvm-build/./bin/clang++ -DCMAKE_ASM_COMPILER=/llvm-build/./bin/clang -DCMAKE_LINKER=/llvm-build/./bin/ld.lld -DCMAKE_AR=/llvm-build/./bin/llvm-ar -DCMAKE_RANLIB=/llvm-build/./bin/llvm-ranlib -DCMAKE_NM=/llvm-build/./bin/llvm-nm -DCMAKE_OBJDUMP=/llvm-build/./bin/llvm-objdump -DCMAKE_OBJCOPY=/llvm-build/./bin/llvm-objcopy -DCMAKE_STRIP=/llvm-build/./bin/llvm-strip -DCMAKE_READELF=/llvm-build/./bin/llvm-readelf -DCMAKE_C_COMPILER_TARGET=riscv64-unknown-fuchsia -DCMAKE_CXX_COMPILER_TARGET=riscv64-unknown-fuchsia -DCMAKE_ASM_COMPILER_TARGET=riscv64-unknown-fuchsia -DCMAKE_INSTALL_PREFIX= -DLLVM_BINARY_DIR=/llvm-build -DLLVM_CONFIG_PATH=/llvm-build/bin/llvm-config -DLLVM_ENABLE_WERROR=OFF -DLLVM_HOST_TRIPLE=x86_64-unknown-linux-gnu -DLLVM_HAVE_LINK_VERSION_SCRIPT=1 -DLLVM_USE_RELATIVE_PATHS_IN_DEBUG_INFO=OFF -DLLVM_USE_RELATIVE_PATHS_IN_FILES=ON -DLLVM_LIT_ARGS=-sv -DLLVM_SOURCE_PREFIX= -DPACKAGE_VERSION=17.0.0git -DCMAKE_BUILD_TYPE=Release -DCMAKE_MAKE_PROGRAM=/usr/local/bin/ninja -DCMAKE_EXPORT_COMPILE_COMMANDS=1 -DCOMPILER_RT_BUILD_BUILTINS=OFF -DLLVM_INCLUDE_TESTS=ON -DLLVM_ENABLE_PROJECTS_USED=ON -DLLVM_ENABLE_PER_TARGET_RUNTIME_DIR=ON -DCMAKE_C_COMPILER_WORKS=ON -DCMAKE_CXX_COMPILER_WORKS=ON -DCMAKE_ASM_COMPILER_WORKS=ON -DCOMPILER_RT_DEFAULT_TARGET_ONLY=ON -DLLVM_RUNTIMES_TARGET=riscv64-unknown-fuchsia -DHAVE_LLVM_LIT=ON -DLLVM_DEFAULT_TARGET_TRIPLE=riscv64-unknown-fuchsia "-DLLVM_ENABLE_RUNTIMES=compiler-rt;libcxx;libcxxabi;libunwind" -DLLVM_USE_LINKER=lld "-DCMAKE_ASM_FLAGS=--target=riscv64-unknown-fuchsia -I/fuchsia-idk/pkg/sync/include -I/fuchsia-idk/pkg/fdio/include" -DCMAKE_BUILD_TYPE=RelWithDebInfo -DCMAKE_BUILD_WITH_INSTALL_RPATH=ON "-DCMAKE_CXX_FLAGS=--target=riscv64-unknown-fuchsia -I/fuchsia-idk/pkg/sync/include -I/fuchsia-idk/pkg/fdio/include" "-DCMAKE_C_FLAGS=--target=riscv64-unknown-fuchsia -I/fuchsia-idk/pkg/sync/include -I/fuchsia-idk/pkg/fdio/include" -DCMAKE_EXE_LINKER_FLAGS=-L/fuchsia-idk/arch/riscv64/lib -DCMAKE_MODULE_LINKER_FLAGS=-L/fuchsia-idk/arch/riscv64/lib -DCMAKE_SHARED_LINKER_FLAGS=-L/fuchsia-idk/arch/riscv64/lib -DCMAKE_SYSROOT=/fuchsia-idk/arch/riscv64/sysroot -DCMAKE_SYSTEM_NAME=Fuchsia -DCOMPILER_RT_CXX_LIBRARY=libcxx -DCOMPILER_RT_USE_BUILTINS_LIBRARY=ON -DCOMPILER_RT_USE_LLVM_UNWINDER=ON -DLIBCXXABI_HERMETIC_STATIC_LIBRARY=ON -DLIBCXXABI_INSTALL_STATIC_LIBRARY=OFF -DLIBCXXABI_USE_COMPILER_RT=ON -DLIBCXXABI_USE_LLVM_UNWINDER=ON -DLIBCXX_ABI_VERSION=2 -DLIBCXX_ENABLE_STATIC_ABI_LIBRARY=ON -DLIBCXX_HERMETIC_STATIC_LIBRARY=ON -DLIBCXX_STATICALLY_LINK_ABI_IN_SHARED_LIBRARY=OFF -DLIBCXX_USE_COMPILER_RT=ON -DLIBUNWIND_HIDE_SYMBOLS=ON -DLIBUNWIND_USE_COMPILER_RT=ON -DLLVM_ENABLE_ASSERTIONS=OFF "-DLLVM_ENABLE_RUNTIMES=compiler-rt;libcxx;libcxxabi;libunwind" -GNinja /llvm-project/llvm/runtimes/../../runtimes && /usr/bin/cmake -E touch /llvm-build/runtimes/runtimes-riscv64-unknown-fuchsia-stamps//runtimes-riscv64-unknown-fuchsia-configure
ninja: build stopped: subcommand failed.

[petrhosek]

We're currently in an interim state where we're bringing up Fuchsia on RISC-V but don't yet include RISC-V sysroot in our SDK because it's not ready yet. To workaround this, we have a script that can generate an artificial SDK stubs for RISC-V which is needed here. To use it, you'll need need the following invocation on line 105:

${FUCHSIA_SRCDIR}/scripts/clang/generate_sysroot.py --sdk-dir=${IDK_DIR} --arch=riscv64 --ifs-path=${FUCHSIA_SRCDIR}/prebuilt/third_party/clang/linux-x64/bin/llvm-ifs

[cclauss]

Suggested change

	The LLVM toolchain that Fuchsia uses has a couple additionaly dependencies,
	The LLVM toolchain that Fuchsia uses has a couple of additional dependencies,