Runtimes: build Runtime and StringProcessing with whole module...

...optimization in Apple vendor configurations.

This is needed to avoid increasing the
size of the associated dylibs.

Take this chance to remove the `-enable-ossa-modules` flag when building
Runtimes, since that's a noop now.

Addresses rdar://165699017

Author: edymtt

Runtimes/Supplemental/Runtime/CMakeLists.txt

@@ -88,7 +88,6 @@ add_compile_options(
   "$<$<COMPILE_LANGUAGE:Swift>:SHELL:-enable-experimental-feature LifetimeDependenceMutableAccessors>"
   "$<$<COMPILE_LANGUAGE:Swift>:SHELL:-disable-upcoming-feature MemberImportVisibility>"
   "$<$<COMPILE_LANGUAGE:Swift>:SHELL:-Xfrontend -enable-lexical-lifetimes=false>"
-  "$<$<COMPILE_LANGUAGE:Swift>:SHELL:-Xfrontend -enable-ossa-modules>"
   "$<$<COMPILE_LANGUAGE:Swift>:-warn-implicit-overrides>"
   "$<$<COMPILE_LANGUAGE:Swift>:-cxx-interoperability-mode=default>"
   "$<$<COMPILE_LANGUAGE:Swift>:SHELL:-Xfrontend -experimental-spi-only-imports>"

Runtimes/Supplemental/Runtime/cmake/caches/Vendors/Apple/apple-common.cmake

@@ -1,5 +1,6 @@
 set(CMAKE_BUILD_TYPE RelWithDebInfo CACHE STRING "")
 set(BUILD_SHARED_LIBS YES CACHE BOOL "")
+set(CMAKE_Swift_COMPILATION_MODE wholemodule CACHE STRING "")
 set(SwiftRuntime_INSTALL_NESTED_SUBDIR OFF CACHE BOOL "")
 
 set(CMAKE_CXX_FLAGS_MINSIZEREL "-Os -g -DNDEBUG" CACHE STRING "")