runtime/cgo: add .file directive to GNU assembly files

runtime/cgo: add .file directive to GNU assembly files

Without it, at least on ARM64 with older BFD linker, it will
include the file of the object file (which is of a temporary path)
as a debug symbol into the binary, causing the build to be
nondeterministic. Adding a .file directive makes it to create a
STT_FILE symbol with deterministic input, and prevent the linker
creating one using the temporary object file path.

Fixes #57035.

Change-Id: I3ab716b240f60f7a891af2f7e10b467df67d1f31
Reviewed-on: https://go-review.googlesource.com/c/go/+/454838
Reviewed-by: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Cherry Mui <cherryyz@google.com>