Add the following flags when supported by the compiler:
  -gno-record-gcc-switches
  -fdebug-prefix-map=$WORK=/tmp/go-build

Add an empty NAME symbol to the ELF .symtab. GNU ld will add a NAME
symbol when one is not present; including one of our own prevents it
from adding a reference to the link tempdir.

Fixes #13247 for compilers that support -fdebug-prefix-map. (gcc, clang
in the near future.)

Change-Id: I221c71fc59cd23ee8c99bcc038793ff4623c9ffc
Reviewed-on: https://go-review.googlesource.com/19363Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Damien Neil <dneil@google.com>