cmake: Establish dependency on utils/availability-macros.def

Author: slavapestov

Runtimes/Core/cmake/modules/AvailabilityMacros.cmake

@@ -1,4 +1,7 @@
-file(STRINGS "${SwiftCore_SWIFTC_SOURCE_DIR}/utils/availability-macros.def" availability_defs)
+configure_file("${SwiftCore_SWIFTC_SOURCE_DIR}/utils/availability-macros.def"
+               "${CMAKE_CURRENT_BINARY_DIR}/availability-macros.def"
+               COPYONLY)
+file(STRINGS "${CMAKE_CURRENT_BINARY_DIR}/availability-macros.def" availability_defs)
 list(FILTER availability_defs EXCLUDE REGEX "^\\s*(#.*)?$")
 foreach(def ${availability_defs})
   add_compile_options("$<$<COMPILE_LANGUAGE:Swift>:SHELL:-Xfrontend -define-availability -Xfrontend \"${def}\">")