Fix UpdateChromeANGLE on mac for debug angle Update script to copy libABSL, libC++ and google_zLIB optionally Add in check before removing nonexistant files Tested by running script after building ANGLE Bug: angleproject:1944 Change-Id: I532d055b7fc70f58ebd807e7e203e4fa6a86be0e Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3466777 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Yuly Novikov <ynovikov@chromium.org>