Re-enable the "gccgo" build target

Use a workaround from https://github.com/golang/go/issues/15628 for
issues with newer-style vendoring in gcc-go.

Travis's trusty images have gcc-go 4.9, which implements Go 1.2, so it's
missing sync.Pool (introduced in 1.3), so we can't enable the test
there.

Signed-off-by: Nalin Dahyabhai <nalin@redhat.com>

hack/make.sh

@@ -39,7 +39,7 @@ DEFAULT_BUNDLES=(
 
 	test-unit
 
-	#gccgo -- failing due to 1.7 incompatibilities
+	gccgo
 	cross
 )
 

hack/make/gccgo

@@ -7,6 +7,7 @@ BINARY_FULLNAME="$BINARY_NAME$BINARY_EXTENSION"
 
 source "${MAKEDIR}/.go-autogen"
 
+export GCCGO=${SCRIPTDIR}/../vagrant/gccgo-wrapper.sh
 # gccgo require explicit flag -pthread to allow goroutines to work.
 go build -compiler=gccgo \
 	-o "$DEST/$BINARY_FULLNAME" \

vagrant/gccgo-wrapper.sh

@@ -0,0 +1,9 @@
+#!/bin/bash
+additional=
+for arg in "$@" ; do
+	if test -d "$arg"/github.com/containers/storage ; then
+		additional="$additional -I $arg/github.com/containers/storage/vendor"
+	fi
+done
+echo gccgo $additional "$@" > /tmp/gccgo
+gccgo $additional "$@"