Limit cleanup of .gc{no,da} files to src and scripts subfolders

Other folders in the build tree might not be related to the strongSwan tree,
or are not even accessible.

Makefile.am

@@ -39,7 +39,7 @@ apidoc :	Doxyfile
 
 cov-reset-common:
 		@rm -rf $(top_builddir)/coverage
-		@find $(top_builddir) -name "*.gcda" -delete
+		@find $(top_builddir)/{src,scripts} -name "*.gcda" -delete
 
 if COVERAGE
 cov-reset: cov-reset-common
@@ -67,7 +67,7 @@ coverage:
 endif
 
 clean-local: cov-reset-common
-		@find $(top_builddir) -name "*.gcno" -delete
+		@find $(top_builddir)/{src,scripts} -name "*.gcno" -delete
 		@rm -rf apidoc
 
 .PHONY: cov-reset-common cov-reset cov-report coverage