Added env in case not bourne shell

git-svn-id: http://svn.savannah.nongnu.org/svn/rdiff-backup@340 2b77aa54-bcbc-44c9-a7ec-4f6cf2b41109

trunk/rdiff-backup/FAQ-body.html

@@ -149,7 +149,7 @@ these instructions build it fine with all tests running OK
 	aclocal
 	autoconf
 	automake --foreign --add-missing
-	CFLAGS=-no-cpp-precomp ./configure
+	env CFLAGS=-no-cpp-precomp ./configure
 	make
 	make install
 </pre>