cfg.mak: ignore trailing whitespace in gnulib local patches

The diff files in gnulib/local may well contain trailing whitespace.
They are simply diff's of gnulib code which should not be modified to
follow libvirt style rules.
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>

cfg.mk

@@ -1224,7 +1224,7 @@ exclude_file_name_regexp--sc_require_config_h_first = \
 	^(examples/|tools/virsh-edit\.c$$)
 
 exclude_file_name_regexp--sc_trailing_blank = \
-  /qemuhelpdata/|/sysinfodata/.*\.data|/virhostcpudata/.*\.cpuinfo$$
+  /qemuhelpdata/|/sysinfodata/.*\.data|/virhostcpudata/.*\.cpuinfo|^gnulib/local/.*/.*diff$$
 
 exclude_file_name_regexp--sc_unmarked_diagnostics = \
   ^(docs/apibuild.py|tests/virt-aa-helper-test|docs/js/.*\.js)$$