[Linux] Enable build IDs.

We should use build IDs on Linux so that we can identify the built
artefacts, and also so that we can match them up with debug
information should we choose to separate it.

rdar://130582819

Author: al45tair

CMakeLists.txt

@@ -122,6 +122,7 @@ include(CheckCSourceCompiles)
 include(CheckFunctionExists)
 include(CheckIncludeFiles)
 include(CheckLibraryExists)
+include(CheckLinkerFlag)
 include(CheckSymbolExists)
 include(GNUInstallDirs)
 include(CTest)
@@ -175,6 +176,8 @@ option(ENABLE_THREAD_LOCAL_STORAGE "enable usage of thread local storage via _Th
 set(DISPATCH_USE_THREAD_LOCAL_STORAGE ${ENABLE_THREAD_LOCAL_STORAGE})
 
 
+check_linker_flag(C "LINKER:-build-id=sha1" LINKER_SUPPORTS_BUILD_ID)
+
 check_symbol_exists(__GNU_LIBRARY__ "features.h" _GNU_SOURCE)
 if(_GNU_SOURCE)
   set(CMAKE_REQUIRED_DEFINITIONS ${CMAKE_REQUIRED_DEFINITIONS} -D_GNU_SOURCE)

src/BlocksRuntime/CMakeLists.txt

@@ -22,6 +22,10 @@ endif()
 set_target_properties(BlocksRuntime PROPERTIES
   POSITION_INDEPENDENT_CODE TRUE)
 
+if(LINKER_SUPPORTS_BUILD_ID)
+  target_link_options(BlocksRuntime PRIVATE "LINKER:-build-id=sha1")
+endif()
+
 add_library(BlocksRuntime::BlocksRuntime ALIAS BlocksRuntime)
 
 install(FILES Block.h

src/CMakeLists.txt

@@ -178,6 +178,10 @@ if(NOT CMAKE_SYSTEM_NAME MATCHES "Darwin|Windows")
   set_target_properties(dispatch PROPERTIES INSTALL_RPATH "$ORIGIN")
 endif()
 
+if(LINKER_SUPPORTS_BUILD_ID)
+  target_link_options(dispatch PRIVATE "LINKER:-build-id=sha1")
+endif()
+
 if(ENABLE_SWIFT)
   add_subdirectory(swift)
 endif()