templates/15-gomod.sh: fix mkdir issues (#57)

Previously when a package uses gomod template multiple times, sub-packages
built after the first one would fail because $SRCDIR/abbuild exists.

This patch fixes mkdir errors by adding -p option to mkdir, avoiding re-
creation of subdirs and returning errors when $SRCDIR/abbuild has already
been created by previous builds.

Author: handsomexdd1024

templates/15-gomod.sh

@@ -27,7 +27,7 @@ build_gomod_configure() {
 		abdie "ABSHADOW must be set to true for this build type: $?."
 	fi
 
-	mkdir "$BLDDIR" \
+	mkdir -pv "$BLDDIR" \
 		|| abdie "Failed to create $SRCDIR/abbuild: $?."
 	cd "$BLDDIR" \
 		|| abdie "Failed to cd $SRCDIR/abbuild: $?."