Update cmake/modules/AddSwiftUnittests.cmake

Co-authored-by: Eric Miotto <[email protected]>

Author: lorentey

cmake/modules/AddSwiftUnittests.cmake

@@ -40,7 +40,9 @@ function(add_swift_unittest test_dirname)
   endif()
 
   if("${CMAKE_SYSTEM_NAME}" STREQUAL "Darwin")
-    # Add an @rpath to the swift library directory.
+    # Add an @rpath to the swift library directory
+    # and one to the OS dylibs we require but
+    # are not building ourselves (e.g Foundation overlay)
     set_target_properties(${test_dirname} PROPERTIES
       BUILD_RPATH "${SWIFT_LIBRARY_OUTPUT_INTDIR}/swift/macosx;${SWIFT_DARWIN_STDLIB_INSTALL_NAME_DIR}")
     # Force all the swift libraries to be found via rpath.
@@ -87,4 +89,3 @@ function(add_swift_unittest test_dirname)
   endif()
 endfunction()
 
-