Support tools/src/fileutils on macos

Change-Id: Ibfb6b92f0df14822994a5c355f6d2044326f7028
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/53080
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: James Price <jrprice@google.com>
diff --git a/tools/src/fileutils/fileutils_linux.go b/tools/src/fileutils/fileutils_other.go
similarity index 100%
rename from tools/src/fileutils/fileutils_linux.go
rename to tools/src/fileutils/fileutils_other.go