binman: Exclude dist-packages and site-packages

Newer versions of the python3-coverage tool require a directory
separator before and after the directory name. Add this so that system
package are not included in the coverage report.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/u_boot_pylib/test_util.py b/tools/u_boot_pylib/test_util.py
index dd67196..ed216c4f 100644
--- a/tools/u_boot_pylib/test_util.py
+++ b/tools/u_boot_pylib/test_util.py
@@ -56,7 +56,7 @@
     else:
         glob_list = []
     glob_list += exclude_list
-    glob_list += ['*libfdt.py', '*site-packages*', '*dist-packages*']
+    glob_list += ['*libfdt.py', '*/site-packages/*', '*/dist-packages/*']
     glob_list += ['*concurrencytest*']
     test_cmd = 'test' if 'binman' in prog or 'patman' in prog else '-t'
     prefix = ''