cmake: add USE_SYSTEM_* options (#153)

Similar to the work done in pytorch/pytorch#37137, this adds the following CMake options:

- `USE_SYSTEM_LIBS`
- `USE_SYSTEM_GOOGLEBENCHMARK`
- `USE_SYSTEM_GOOGLETEST`

This is particularly useful in the context of Nix, where we can build these libraries once and then re-use them elsewhere to avoid rebuilding vendors dependencies.

Author: ConnorBaker

CMakeLists.txt

@@ -23,6 +23,9 @@ OPTION(CPUINFO_BUILD_UNIT_TESTS "Build cpuinfo unit tests" ON)
 OPTION(CPUINFO_BUILD_MOCK_TESTS "Build cpuinfo mock tests" ON)
 OPTION(CPUINFO_BUILD_BENCHMARKS "Build cpuinfo micro-benchmarks" ON)
 OPTION(CPUINFO_BUILD_PKG_CONFIG "Build pkg-config manifest" ON)
+OPTION(USE_SYSTEM_LIBS "Use system libraries instead of downloading and building them" OFF)
+OPTION(USE_SYSTEM_GOOGLEBENCHMARK "Use system Google Benchmark library instead of downloading and building it" ${USE_SYSTEM_LIBS})
+OPTION(USE_SYSTEM_GOOGLETEST "Use system Google Test library instead of downloading and building it" ${USE_SYSTEM_LIBS})
 
 # ---[ CMake options
 INCLUDE(GNUInstallDirs)
@@ -117,8 +120,10 @@ SET(CONFU_DEPENDENCIES_SOURCE_DIR ${CMAKE_SOURCE_DIR}/deps
 SET(CONFU_DEPENDENCIES_BINARY_DIR ${CMAKE_BINARY_DIR}/deps
   CACHE PATH "Confu-style dependencies binary directory")
 
-IF(CPUINFO_BUILD_MOCK_TESTS OR CPUINFO_BUILD_UNIT_TESTS)
-  IF(CPUINFO_SUPPORTED_PLATFORM AND NOT DEFINED GOOGLETEST_SOURCE_DIR)
+IF(CPUINFO_SUPPORTED_PLATFORM AND (CPUINFO_BUILD_MOCK_TESTS OR CPUINFO_BUILD_UNIT_TESTS))
+  IF(USE_SYSTEM_GOOGLETEST)
+    FIND_PACKAGE(GTest REQUIRED)
+  ELSEIF(NOT DEFINED GOOGLETEST_SOURCE_DIR)
     MESSAGE(STATUS "Downloading Google Test to ${CONFU_DEPENDENCIES_SOURCE_DIR}/googletest (define GOOGLETEST_SOURCE_DIR to avoid it)")
     CONFIGURE_FILE(cmake/DownloadGoogleTest.cmake "${CONFU_DEPENDENCIES_BINARY_DIR}/googletest-download/CMakeLists.txt")
     EXECUTE_PROCESS(COMMAND "${CMAKE_COMMAND}" -G "${CMAKE_GENERATOR}" .
@@ -129,8 +134,10 @@ IF(CPUINFO_BUILD_MOCK_TESTS OR CPUINFO_BUILD_UNIT_TESTS)
   ENDIF()
 ENDIF()
 
-IF(CPUINFO_BUILD_BENCHMARKS)
-  IF(CPUINFO_SUPPORTED_PLATFORM AND NOT DEFINED GOOGLEBENCHMARK_SOURCE_DIR)
+IF(CPUINFO_SUPPORTED_PLATFORM AND CPUINFO_BUILD_BENCHMARKS)
+  IF(USE_SYSTEM_GOOGLEBENCHMARK)
+    FIND_PACKAGE(benchmark REQUIRED)
+  ELSEIF(NOT DEFINED GOOGLEBENCHMARK_SOURCE_DIR)
     MESSAGE(STATUS "Downloading Google Benchmark to ${CONFU_DEPENDENCIES_SOURCE_DIR}/googlebenchmark (define GOOGLEBENCHMARK_SOURCE_DIR to avoid it)")
     CONFIGURE_FILE(cmake/DownloadGoogleBenchmark.cmake "${CONFU_DEPENDENCIES_BINARY_DIR}/googlebenchmark-download/CMakeLists.txt")
     EXECUTE_PROCESS(COMMAND "${CMAKE_COMMAND}" -G "${CMAKE_GENERATOR}" .
@@ -308,7 +315,7 @@ INSTALL(EXPORT cpuinfo-targets
 # ---[ cpuinfo micro-benchmarks
 IF(CPUINFO_SUPPORTED_PLATFORM AND CPUINFO_BUILD_BENCHMARKS)
   # ---[ Build google benchmark
-  IF(NOT TARGET benchmark)
+  IF(NOT TARGET benchmark AND NOT USE_SYSTEM_GOOGLEBENCHMARK)
     SET(BENCHMARK_ENABLE_TESTING OFF CACHE BOOL "")
     ADD_SUBDIRECTORY(
       "${GOOGLEBENCHMARK_SOURCE_DIR}"
@@ -327,7 +334,7 @@ ENDIF()
 IF(CPUINFO_SUPPORTED_PLATFORM)
   IF(CPUINFO_BUILD_MOCK_TESTS OR CPUINFO_BUILD_UNIT_TESTS)
     # ---[ Build google test
-    IF(NOT TARGET gtest)
+    IF(NOT TARGET gtest AND NOT USE_SYSTEM_GOOGLETEST)
       IF(MSVC AND NOT CPUINFO_RUNTIME_TYPE STREQUAL "static")
         SET(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
       ENDIF()

deps/clog/CMakeLists.txt

@@ -14,6 +14,8 @@ ELSE()
   OPTION(CLOG_LOG_TO_STDIO "Log errors, warnings, and information to stdout/stderr" ON)
 ENDIF()
 OPTION(CLOG_BUILD_TESTS "Build clog tests" ON)
+OPTION(USE_SYSTEM_LIBS "Use system libraries instead of downloading and building them" OFF)
+OPTION(USE_SYSTEM_GOOGLETEST "Use system Google Test library instead of downloading and building it" ${USE_SYSTEM_LIBS})
 
 # ---[ CMake options
 IF(CLOG_BUILD_TESTS)
@@ -39,7 +41,9 @@ SET(CONFU_DEPENDENCIES_BINARY_DIR ${CMAKE_BINARY_DIR}/deps
   CACHE PATH "Confu-style dependencies binary directory")
 
 IF(CLOG_BUILD_TESTS)
-  IF(NOT DEFINED GOOGLETEST_SOURCE_DIR)
+  IF(USE_SYSTEM_GOOGLETEST)
+    FIND_PACKAGE(GTest REQUIRED)
+  ELSEIF(NOT DEFINED GOOGLETEST_SOURCE_DIR)
     MESSAGE(STATUS "Downloading Google Test to ${CONFU_DEPENDENCIES_SOURCE_DIR}/googletest (define GOOGLETEST_SOURCE_DIR to avoid it)")
     CONFIGURE_FILE(cmake/DownloadGoogleTest.cmake "${CONFU_DEPENDENCIES_BINARY_DIR}/googletest-download/CMakeLists.txt")
     EXECUTE_PROCESS(COMMAND "${CMAKE_COMMAND}" -G "${CMAKE_GENERATOR}" .
@@ -78,7 +82,7 @@ INSTALL(TARGETS clog
 # ---[ clog tests
 IF(CLOG_BUILD_TESTS)
   # ---[ Build google test
-  IF(NOT TARGET gtest)
+  IF(NOT TARGET gtest AND NOT USE_SYSTEM_GOOGLETEST)
     IF(MSVC AND NOT CLOG_RUNTIME_TYPE STREQUAL "static")
       SET(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
     ENDIF()