[cmake] Make sure SOURCEKIT_DEPLOYMENT_OS is only set once, at the top.

Reset Darwin specific CMake variables to match the correct
SDK and architecture. This is needed when cross compiling, or we'll end up with
conflicting SDK and architectures.

Remove unused variable SOURCEKIT_GLOBAL_DEPLOYMENT_TARGET_FLAGS.

Author: Doug Coleman

tools/SourceKit/CMakeLists.txt

@@ -20,6 +20,14 @@ configure_file(
 set(SOURCEKIT_DEPLOYMENT_OS "${SWIFT_HOST_VARIANT}")
 set(SOURCEKIT_DEPLOYMENT_TARGET "${SWIFT_SDK_${SWIFT_HOST_VARIANT_SDK}_DEPLOYMENT_VERSION}")
 
+swift_is_installing_component(sourcekit-inproc SOURCEKIT_INSTALLING_INPROC)
+
+if("${CMAKE_SYSTEM_NAME}" STREQUAL "Darwin")
+  set(CMAKE_OSX_SYSROOT "${SWIFT_SDK_${SWIFT_HOST_VARIANT_SDK}_PATH}")
+  set(CMAKE_OSX_ARCHITECTURES "${SWIFT_HOST_VARIANT_ARCH}")
+  set(CMAKE_OSX_DEPLOYMENT_TARGET "")
+endif()
+
 function(add_sourcekit_symbol_exports target_name export_file)
   # Makefile.rules contains special cases for different platforms.
   # We restrict ourselves to Darwin for the time being.
@@ -458,10 +466,6 @@ if("${CMAKE_SYSTEM_NAME}" STREQUAL "Darwin")
     string(REGEX MATCH "[0-9]+\\.[0-9]+" SOURCEKIT_DEPLOYMENT_TARGET ${SOURCEKIT_DEPLOYMENT_TARGET})
   endif()
 
-  # Choose a deployment OS if none was set.
-  set(SOURCEKIT_DEPLOYMENT_OS "macosx" CACHE STRING
-      "Deployment OS for SourceKit [macosx, iphoneos, iphonesimulator].")
-
   # Sadly there are two OS naming conventions.
   # xcrun SDK name:   macosx iphoneos iphonesimulator (+ "internal" or version)
   # -mOS-version-min: macosx ios      ios-simulator
@@ -482,10 +486,6 @@ if("${CMAKE_SYSTEM_NAME}" STREQUAL "Darwin")
     message(FATAL_ERROR "Can't understand SOURCEKIT_DEPLOYMENT_OS '${SOURCEKIT_DEPLOYMENT_OS}';")
   endif()
 
-  # Determine deployment flags for the C/C++ compiler and linker.
-  set(SOURCEKIT_GLOBAL_DEPLOYMENT_TARGET_FLAGS
-    "-m${version_min_os}-version-min=${SOURCEKIT_DEPLOYMENT_TARGET}")
-
   # Add deployment target to C/C++ compiler and linker flags.
   # FIXME: CMAKE_OSX_DEPLOYMENT_TARGET falls over when used for iOS versions.
   if (XCODE)