Reproducible BUILD_PATH_PREFIX_MAP

Make builds reproducible by honoring BUILD_PATH_PREFIX_MAP
Upstream has rejected the patch in this form and promised to implement an
alternative they are happy with instead. That hasn't happened yet though.

Bug: https://github.com/golang/go/issues/22491, https://github.com/golang/go/issues/16860
Forwarded: https://golang.org/cl/73291 (rejected upstream though)

Gbp-Pq: Name 0001-Reproducible-BUILD_PATH_PREFIX_MAP.patch

golang-1.12 (1.12.9-2) unstable; urgency=medium

  * Exclude testdata from dh_makeshlibs.
    Otherwise, the build fails at least on armel and armhf.

[dgit import unpatched golang-1.12 1.12.9-2]

Import golang-1.12_1.12.9-2.debian.tar.xz

[dgit import tarball golang-1.12 1.12.9-2 golang-1.12_1.12.9-2.debian.tar.xz]

Import golang-1.12_1.12.9.orig.tar.gz

[dgit import orig golang-1.12_1.12.9.orig.tar.gz]