[Build][Compatibility] Move compatibility deployment targets to top level.

Moved the compatibility deployment targets to the top level CMakeLists.
Without this, if we build without SWIFT_BUILD_STDLIB set, the threading
library doesn't see the correct values.  This didn't affect local builds
when testing the original fix, but it does affect B&I.

rdar://96690200

Author: al45tair

CMakeLists.txt

@@ -454,6 +454,15 @@ set(SWIFT_DARWIN_DEPLOYMENT_VERSION_TVOS "9.0" CACHE STRING
 set(SWIFT_DARWIN_DEPLOYMENT_VERSION_WATCHOS "2.0" CACHE STRING
     "Minimum deployment target version for watchOS")
 
+#
+#  Compatibility library deployment versions
+#
+
+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")
+
 #
 # User-configurable debugging options.
 #

stdlib/toolchain/CMakeLists.txt

@@ -46,11 +46,6 @@ endif()
 # runtime being patched only through public ABI.
 list(APPEND CXX_COMPILE_FLAGS "-DSWIFT_COMPATIBILITY_LIBRARY=1")
 
-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")
-
 if(SWIFT_STDLIB_SUPPORT_BACK_DEPLOYMENT)
   add_subdirectory(legacy_layouts)
   add_subdirectory(Compatibility50)