Fix make docs rule to work with out-of-tree builds.

git-svn-id: svn://svn.berlios.de/openocd/trunk@1891 b42882b7-edfa-0310-969c-e2dbd0fdcd60

Makefile.am

@@ -16,7 +16,7 @@ EXTRA_DIST = Doxyfile
 docs: pdf html doxygen
 
 doxygen::
-	doxygen Doxyfile 2>&1 | perl tools/logger.pl > doxygen.log
+	(cd $(srcdir) && doxygen Doxyfile 2>&1 | perl tools/logger.pl ) > doxygen.log
 
 doxygen-clean:
 	rm -f -r doxygen doxygen.log