Fix compilation with Mono master

Bugs, bugs everywhere! https://bugzilla.xamarin.com/show_bug.cgi?id=42606

cc.sh

@@ -29,6 +29,10 @@ XBUILD_ARGS+=("/p:Configuration=$BUILD")
 
 cd "$(dirname "$(readlink -f "$0")")"
 
+if [[ -f "mono_envsetup.sh" ]]; then
+	source "mono_envsetup.sh"
+fi
+
 if [[ -d ".git" ]] && hash git &>/dev/null; then
 	git pull || true
 fi