Allow to pass in the use_ccache via go build.

Removes usage of go build tags in favor of passing in
configuration via -ldflags -X ...

BUG=chromium:773875
TEST=unit test

Change-Id: I4e8a58e1679b2858e9d4620d6b9c7a35ad08a6ee
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/1670987
Reviewed-by: George Burgess <gbiv@chromium.org>
Tested-by: Tobias Bosch <tbosch@google.com>
16 files changed