CMake: fix separate overlay builds

When building overlay separately, look for dylibs in the overlay
build directory first, and only then fall back to the compiler resource
directory.

If the overlay changes the ABI, we shouldn't even try the dylibs in the
compiler resource directory, that is certain to fail the build or
result in miscompiles.

rdar://22866170

Swift SVN r32382

cmake/modules/AddSwift.cmake

@@ -1086,7 +1086,7 @@ function(_add_swift_library_single target name)
   set_property(TARGET "${target}" APPEND_STRING PROPERTY
       COMPILE_FLAGS " ${c_compile_flags}")
   set_property(TARGET "${target}" APPEND_STRING PROPERTY
-    LINK_FLAGS " ${link_flags} -L${SWIFT_NATIVE_SWIFT_TOOLS_PATH}/../lib/swift/${SWIFTLIB_SINGLE_SUBDIR} -L${SWIFT_NATIVE_SWIFT_TOOLS_PATH}/../lib/swift/${SWIFT_SDK_${SWIFTLIB_SINGLE_SDK}_LIB_SUBDIR} -L${SWIFTLIB_DIR}/${SWIFTLIB_SINGLE_SUBDIR}")
+    LINK_FLAGS " ${link_flags} -L${SWIFTLIB_DIR}/${SWIFTLIB_SINGLE_SUBDIR} -L${SWIFT_NATIVE_SWIFT_TOOLS_PATH}/../lib/swift/${SWIFTLIB_SINGLE_SUBDIR} -L${SWIFT_NATIVE_SWIFT_TOOLS_PATH}/../lib/swift/${SWIFT_SDK_${SWIFTLIB_SINGLE_SDK}_LIB_SUBDIR}")
   target_link_libraries("${target}" PRIVATE
       ${SWIFTLIB_SINGLE_PRIVATE_LINK_LIBRARIES})
   if(${SWIFTLIB_SINGLE_INTERFACE_LINK_LIBRARIES})
@@ -1101,7 +1101,7 @@ function(_add_swift_library_single target name)
     set_property(TARGET "${target_static}" APPEND_STRING PROPERTY
         COMPILE_FLAGS " ${c_compile_flags}")
     set_property(TARGET "${target_static}" APPEND_STRING PROPERTY
-      LINK_FLAGS " ${link_flags} -L${SWIFT_NATIVE_SWIFT_TOOLS_PATH}/../lib/swift/${SWIFTLIB_SINGLE_SUBDIR} -L${SWIFT_NATIVE_SWIFT_TOOLS_PATH}/../lib/swift/${SWIFT_SDK_${SWIFTLIB_SINGLE_SDK}_LIB_SUBDIR} -L${SWIFTSTATICLIB_DIR}/${SWIFTLIB_SINGLE_SUBDIR}")
+      LINK_FLAGS " ${link_flags} -L${SWIFTSTATICLIB_DIR}/${SWIFTLIB_SINGLE_SUBDIR} -L${SWIFT_NATIVE_SWIFT_TOOLS_PATH}/../lib/swift/${SWIFTLIB_SINGLE_SUBDIR} -L${SWIFT_NATIVE_SWIFT_TOOLS_PATH}/../lib/swift/${SWIFT_SDK_${SWIFTLIB_SINGLE_SDK}_LIB_SUBDIR}")
     target_link_libraries("${target_static}" PRIVATE
         ${SWIFTLIB_SINGLE_PRIVATE_LINK_LIBRARIES})
   endif()