Fix error when installing with <install-source-root> and source file names

are absolute.


[SVN r29180]

tools/build

@@ -1 +1 @@
-Subproject commit 708c904345cc91b9ec59a2d8674e4d42d1380ff3
+Subproject commit 7ef55e8276a53e3063e62c4c4f2f8a0ca32e4e99