rm will error when the file is missing without the -f flag. We delete a
few files without checking that they exist first.

Bug: b/150458033
Change-Id: I5a104d383f59d418eaa55534526194f626c88f57
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2523372Reviewed-by: Geoff Lang <geofflang@chromium.org>