xbps-src: support caching go builds

Piggyback on the existing XBPS_CCACHE logic to enable/disable. Stored in
${XBPS_HOSTDIR}/gocache.

etc/defaults.conf

@@ -39,7 +39,8 @@ XBPS_SUCMD="sudo /bin/sh -c"
 
 # [OPTIONAL]
 # Enable or disable ccache when building packages. The ccache directory
-# is stored in the hostdir, i.e hostdir/ccache.
+# is stored in the hostdir, i.e hostdir/ccache. For go builds this enables
+# caching in hostdir/gocache.
 #
 #XBPS_CCACHE=yes
 

xbps-src

@@ -621,6 +621,10 @@ else
         export CCACHE_COMPILERCHECK=content CCACHE_COMPRESS=1
         export PATH="$CCACHEPATH:$PATH"
         mkdir -p $CCACHE_DIR
+
+        export GOCACHE="${XBPS_HOSTDIR}/gocache"
+    else
+        export GOCACHE=off
     fi
     if [ -n "$XBPS_DISTCC" ]; then
         if [ -n "$XBPS_CCACHE" ]; then