software/gitlab: unset $GOBIN

gitaly's Makefile forcibly sets $GOPATH to install in _build
folder. Once gitaly is built, it is expected to be in _build/bin/gitaly
and copied from there.

With 8eac67a5 (golang: Prepare for future GOPATH removal, 2021-02-26) the
env.sh sets GOBIN, to its own $GOPATH/bin

Since gitaly's build does not set $GOBIN, even if it overrides $GOPATH, the
final bin/gitaly is not in $GOPATH/bin/gitaly (with $GOPATH from Makefile),
but in $GOBIN/gitaly (with $GOBIN from env.sh)

To prevent this, unset $GOBIN before running make, which keeps the old
behavior of only using the $GOPATH from the Makefile

software/gitlab/software.cfg

@@ -268,7 +268,9 @@ configure-command = cd ${:path}/ruby &&
     ${:bundle} config --local build.charlock_holmes --with-icu-dir=${icu:location}
 make-binary =
 make-targets =
-  . ${gowork:env.sh} && make
+  . ${gowork:env.sh} &&
+  unset GOBIN &&
+  make
 environment =
   PKG_CONFIG_PATH=${openssl-1.0:location}/lib/pkgconfig:${icu:location}/lib/pkgconfig
   PATH=${pkgconfig:location}/bin:${ruby2.3:location}/bin:%(PATH)s