Check if an installed file exists and report error if not.

So far there is only one case happened in b/277039235 that an installed file in that product is moved to another directory in LOCAL_POST_INSTALL_CMD. The team agreed to convert to Android.bp, but better to add a check and report the error.

Resend this to check symlinks using os.path.islink(), which doesn't follow the link. os.path.isfile() follows symlinks and returns false since the symlinks are for devices and could not be resolved on host file systems.

Bug: 277039235
Test: m sbom
Test: build/soong/tests/sbom_test.sh
Change-Id: Ia9f1cd24dc974a3e41487bc17c9c76a26d419395