[cmake] Move SwiftApplyXcodeSubstitutions.cmake => SwiftXcodeSupport.cmake.

As an additional fix, this moves the include of SwiftXcodeSupport to the one
place where its functionality is used, AddSwift.cmake. Keeping the include in
./CMakeLists.txt makes it seem like the functionality is needed there (when it
is not).

In a subsequent commit, I am going to refactor the xcode support I have been
adding to SwiftSharedCMakeConfig into this file and have SwiftSharedCMakeConfig
import it.

Author: gottesmm

CMakeLists.txt

@@ -356,7 +356,6 @@ include(AddSwift)
 include(SwiftConfigureSDK)
 include(SwiftInstallComponents)
 include(SwiftGetConfigurationTypes)
-include(SwiftApplyXcodeSubstitutions)
 include(SwiftList)
 
 swift_configure_install_components("${SWIFT_INSTALL_COMPONENTS}")

cmake/modules/AddSwift.cmake

@@ -1,4 +1,5 @@
 include(SwiftList)
+include(SwiftXcodeSupport)
 
 # SWIFTLIB_DIR is the directory in the build tree where Swift resource files
 # should be placed.  Note that $CMAKE_CFG_INTDIR expands to "." for

cmake/modules/SwiftApplyXcodeSubstitutions.cmake renamed to cmake/modules/SwiftXcodeSupport.cmake

@@ -1,3 +1,6 @@
+# This file contains cmake configuration specifically related to support for the
+# Xcode generator in CMake.
+
 function(apply_xcode_substitutions config path result_var_name)
   # Hack to deal with the fact that paths contain the build-time
   # variables. Note that this fix is Xcode-specific.