xpcom standalone rules.

configure.in

@@ -2621,6 +2621,16 @@ if test "$MOZ_MAIL_NEWS"; then
 fi
 AC_SUBST(MOZ_MAIL_NEWS)
 
+dnl xpcom standalone. Disabled by default
+XPCOM_STANDALONE=
+MOZ_ARG_ENABLE_BOOL(xpcom-standalone,
+[  --enable-xpcom-standalone     Build XPCOM Standalone],
+  XPCOM_STANDALONE=1 )
+if test "$XPCOM_STANDALONE"; then
+  AC_DEFINE(XPCOM_STANDALONE)
+fi
+AC_SUBST(XPCOM_STANDALONE)
+
 dnl make sure that we compile in multi-processor support
 NS_MT_SUPPORTED=1
 AC_DEFINE(NS_MT_SUPPORTED)