Add zippering support

Upstream build system zippering support.

Setting the `SWIFT_ENABLE_MACCATALYST` flag will build the compatibility
libraries with zippering enabled.

Note that AppleClang and LLVM Clang use different flags to write
zippered files. The Swift stdlib build doesn't know what clang we're
using, so we can't ask it for the compiler ID to determine which whether
we're using AppleClang or LLVM clang, hence the nasty `execute_process`
trick to figure out whether the compiler that's actually compiling the
stdlib knows about the flag or not.

Author: etcwilde

CMakeLists.txt

@@ -460,6 +460,7 @@ set(COMPATIBILITY_MINIMUM_DEPLOYMENT_VERSION_OSX "10.9")
 set(COMPATIBILITY_MINIMUM_DEPLOYMENT_VERSION_IOS "7.0")
 set(COMPATIBILITY_MINIMUM_DEPLOYMENT_VERSION_TVOS "9.0")
 set(COMPATIBILITY_MINIMUM_DEPLOYMENT_VERSION_WATCHOS "2.0")
+set(COMPATIBILITY_MINIMUM_DEPLOYMENT_VERSION_MACCATALYST "13.1")
 
 #
 # User-configurable debugging options.
@@ -585,6 +586,13 @@ option(SWIFT_THREADING_PACKAGE
    Valid package names are 'pthreads', 'darwin', 'linux', 'win32', 'c11', 'none'
    or the empty string for the SDK default.")
 
+option(SWIFT_ENABLE_MACCATALYST
+  "Build the Standard Library and overlays with MacCatalyst support"
+  FALSE)
+
+set(SWIFT_DARWIN_DEPLOYMENT_VERSION_MACCATALYST "14.5" CACHE STRING
+  "Minimum deployment target version for macCatalyst")
+
 #
 # End of user-configurable options.
 #

stdlib/cmake/modules/AddSwiftStdlib.cmake

@@ -82,7 +82,28 @@ function(_add_target_variant_c_compile_link_flags)
       DEPLOYMENT_VERSION "${DEPLOYMENT_VERSION}")
     list(APPEND result "-target" "${target}")
     if(target_variant)
-      list(APPEND result "-target-variant" "${target_variant}")
+      # Check if the C compiler supports `-target-variant` flag
+      # TODO (etcwilde): This is a massive hack to deal with the fact that we
+      # are lying to cmake about what compiler is being used. Normally we could
+      # use `check_cxx_compiler_flag` here. Unfortunately, that uses a different
+      # compiler since we swap out the C compiler part way through the build.
+      file(WRITE "${CMAKE_BINARY_DIR}/stdlib/empty" "")
+      execute_process(
+        COMMAND
+          "${CMAKE_C_COMPILER}"
+          -Wno-unused-command-line-argument
+          -target-variant x86_64-apple-ios14.5-macabi -x c -c - -o /dev/null
+        INPUT_FILE
+          "${CMAKE_BINARY_DIR}/stdlib/empty"
+        OUTPUT_QUIET ERROR_QUIET
+        RESULT_VARIABLE
+          SUPPORTS_TARGET_VARIANT)
+
+      if(SUPPORTS_TARGET_VARIANT EQUAL 0)
+        list(APPEND result "-target-variant" "${target_variant}")
+      else()
+        list(APPEND result "-darwin-target-variant" "${target_variant}")
+      endif()
     endif()
   endif()
 

stdlib/toolchain/Compatibility51/CMakeLists.txt

@@ -19,6 +19,8 @@ add_swift_target_library("${library_name}" STATIC
   DEPLOYMENT_VERSION_TVOS ${COMPATIBILITY_MINIMUM_DEPLOYMENT_VERSION_TVOS}
   DEPLOYMENT_VERSION_WATCHOS ${COMPATIBILITY_MINIMUM_DEPLOYMENT_VERSION_WATCHOS}
 
+  MACCATALYST_BUILD_FLAVOR "zippered"
+
   INSTALL_IN_COMPONENT compiler
   INSTALL_WITH_SHARED)
 

stdlib/toolchain/Compatibility56/CMakeLists.txt

@@ -27,6 +27,8 @@ add_swift_target_library("${library_name}" STATIC
   DEPLOYMENT_VERSION_TVOS ${COMPATIBILITY_MINIMUM_DEPLOYMENT_VERSION_TVOS}
   DEPLOYMENT_VERSION_WATCHOS ${COMPATIBILITY_MINIMUM_DEPLOYMENT_VERSION_WATCHOS}
 
+  MACCATALYST_BUILD_FLAVOR "zippered"
+
   INSTALL_IN_COMPONENT compiler
   INSTALL_WITH_SHARED)
 

stdlib/toolchain/CompatibilityConcurrency/CMakeLists.txt

@@ -14,6 +14,8 @@ add_swift_target_library("${library_name}" STATIC
   DEPLOYMENT_VERSION_TVOS ${COMPATIBILITY_MINIMUM_DEPLOYMENT_VERSION_TVOS}
   DEPLOYMENT_VERSION_WATCHOS ${COMPATIBILITY_MINIMUM_DEPLOYMENT_VERSION_WATCHOS}
 
+  MACCATALYST_BUILD_FLAVOR "zippered"
+
   INSTALL_IN_COMPONENT compiler
   INSTALL_WITH_SHARED)
 

stdlib/toolchain/CompatibilityThreading/CMakeLists.txt

@@ -11,4 +11,6 @@ add_swift_target_library(swiftCompatibilityThreading OBJECT_LIBRARY
   DEPLOYMENT_VERSION_OSX ${COMPATIBILITY_MINIMUM_DEPLOYMENT_VERSION_OSX}
   DEPLOYMENT_VERSION_IOS ${COMPATIBILITY_MINIMUM_DEPLOYMENT_VERSION_IOS}
   DEPLOYMENT_VERSION_TVOS ${COMPATIBILITY_MINIMUM_DEPLOYMENT_VERSION_TVOS}
-  DEPLOYMENT_VERSION_WATCHOS ${COMPATIBILITY_MINIMUM_DEPLOYMENT_VERSION_WATCHOS})
+  DEPLOYMENT_VERSION_WATCHOS ${COMPATIBILITY_MINIMUM_DEPLOYMENT_VERSION_WATCHOS}
+
+  MACCATALYST_BUILD_FLAVOR "zippered")