Cleanup WMO forcing

This patch cleans up the handling of WMO-forcing in the workaround file.
`-wmo` is passed in each of the link jobs in the non-CMP0157-enabled
configuration to keep it matching the behavior of the CMP0157-enabled
builds.

This also moves the commentary about num-threads and WMO to the top of
the file to make it clearer what is going on. Ideally the file wouldn't
have to exist, but it does.

The file also contains the target install-name fix that landed in CMake
3.29.8 and CMake 3.30.2, so earlier versions of CMake 3.29 will work
with this build as well.

Author: etcwilde

Runtimes/Core/cmake/modules/CMakeWorkarounds.cmake

@@ -1,10 +1,15 @@
 # This file contains workarounds for dealing with bugs between CMake and the
 # Swift compiler.
 
-# FIXME: This is a workaround for the broken Swift compiler that cannot
-#        typecheck the Swift stdlib without crashing. <ADD RADAR HERE>.
-#        This is manipulating undocumented CMake-internal variables that may
-#        change behavior at any time and should not be relied on.
+# This is a workaround to avoid crashing the Swift compiler while typechecking
+# swiftCore. The Swift compiler must be run num-threads=0 with WMO in all build
+# configurations.
+# These must be set in CMake _before_ the Swift language is enabled.
+# This is manipulating undocumented CMake-internal variables that may change
+# behavior at any time and should not be relied on.
+# Otherwise CMake will generate the build graph incorrectly for this setup.
+# Ideally this file should not need to exist.
+
 set(CMAKE_Swift_NUM_THREADS 0)
 if(POLICY CMP0157)
   set(CMAKE_Swift_COMPILE_OBJECT "<CMAKE_Swift_COMPILER> -num-threads ${CMAKE_Swift_NUM_THREADS} -c <DEFINES> <FLAGS> <INCLUDES> <SOURCE>")
@@ -18,14 +23,12 @@ if(POLICY CMP0157)
   set(CMAKE_Swift_LINK_EXECUTABLE "<CMAKE_Swift_COMPILER> -num-threads ${SwiftStdlib_NUM_LINK_JOBS} -emit-executable -o <TARGET> <FLAGS> <OBJECTS> <LINK_FLAGS> <LINK_LIBRARIES>")
   set(CMAKE_Swift_CREATE_SHARED_LIBRARY "<CMAKE_Swift_COMPILER> -num-threads ${SwiftStdlib_NUM_LINK_JOBS} -emit-library <CMAKE_SHARED_LIBRARY_Swift_FLAGS> <LANGUAGE_COMPILE_FLAGS> <LINK_FLAGS> ${CMAKE_Swift_IMPLIB_LINKER_FLAGS} <SONAME_FLAG> <TARGET_INSTALLNAME_DIR><TARGET_SONAME> -o <TARGET> <OBJECTS> <LINK_LIBRARIES>")
 else()
-  set(CMAKE_Swift_CREATE_SHARED_LIBRARY "<CMAKE_Swift_COMPILER> -num-threads ${CMAKE_Swift_NUM_THREADS} -emit-library -o <TARGET> -module-name <SWIFT_MODULE_NAME> -module-link-name <SWIFT_LIBRARY_NAME> -emit-module -emit-module-path <SWIFT_MODULE> -emit-dependencies <DEFINES> <FLAGS> <INCLUDES> <SWIFT_SOURCES> <LINK_FLAGS> <SONAME_FLAG> <TARGET_INSTALLNAME_DIR><TARGET_SONAME> ${CMAKE_Swift_IMPLIB_LINKER_FLAGS} <LINK_LIBRARIES>")
+  set(CMAKE_Swift_CREATE_SHARED_LIBRARY "<CMAKE_Swift_COMPILER> -wmo -num-threads ${CMAKE_Swift_NUM_THREADS} -emit-library -o <TARGET> -module-name <SWIFT_MODULE_NAME> -module-link-name <SWIFT_LIBRARY_NAME> -emit-module -emit-module-path <SWIFT_MODULE> -emit-dependencies <DEFINES> <FLAGS> <INCLUDES> <SWIFT_SOURCES> <LINK_FLAGS> <SONAME_FLAG> <TARGET_INSTALLNAME_DIR><TARGET_SONAME> ${CMAKE_Swift_IMPLIB_LINKER_FLAGS} <LINK_LIBRARIES>")
 
-  set(CMAKE_Swift_LINK_EXECUTABLE "<CMAKE_Swift_COMPILER> -num-threads ${CMAKE_Swift_NUM_THREADS} -emit-executable -o <TARGET> -emit-dependencies <DEFINES> <FLAGS> <INCLUDES> <SWIFT_SOURCES> <LINK_FLAGS> <LINK_LIBRARIES>")
+  set(CMAKE_Swift_LINK_EXECUTABLE "<CMAKE_Swift_COMPILER> -wmo -num-threads ${CMAKE_Swift_NUM_THREADS} -emit-executable -o <TARGET> -emit-dependencies <DEFINES> <FLAGS> <INCLUDES> <SWIFT_SOURCES> <LINK_FLAGS> <LINK_LIBRARIES>")
 
-  set(CMAKE_Swift_CREATE_STATIC_LIBRARY "<CMAKE_Swift_COMPILER> -num-threads ${CMAKE_Swift_NUM_THREADS} -emit-library -static -o <TARGET> -module-name <SWIFT_MODULE_NAME> -module-link-name <SWIFT_LIBRARY_NAME> -emit-module -emit-module-path <SWIFT_MODULE> -emit-dependencies <DEFINES> <FLAGS> <INCLUDES> <SWIFT_SOURCES> <LINK_FLAGS> <LINK_LIBRARIES>")
+  set(CMAKE_Swift_CREATE_STATIC_LIBRARY "<CMAKE_Swift_COMPILER> -wmo -num-threads ${CMAKE_Swift_NUM_THREADS} -emit-library -static -o <TARGET> -module-name <SWIFT_MODULE_NAME> -module-link-name <SWIFT_LIBRARY_NAME> -emit-module -emit-module-path <SWIFT_MODULE> -emit-dependencies <DEFINES> <FLAGS> <INCLUDES> <SWIFT_SOURCES> <LINK_FLAGS> <LINK_LIBRARIES>")
 
   set(CMAKE_Swift_ARCHIVE_CREATE "<CMAKE_AR> crs <TARGET> <OBJECTS>")
   set(CMAKE_Swift_ARCHIVE_FINISH "")
-
-  add_compile_options($<$<COMPILE_LANGUAGE:Swift>:-wmo>)
 endif()