Move isFileTarget() to bazel_util.go

Move to common util file so that it may be used by other exporters.

Bug: skia:13485
Change-Id: I3a9833fe6d5ac55548481c93c7805779a374affc
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/566437
Reviewed-by: Kevin Lubick <kjlubick@google.com>
4 files changed