cronet import: exclude .gitignore from import

Test: none
Change-Id: I79200198264a54f517a18a3cfbc77030e89f3401
diff --git a/Cronet/tools/import/copy.bara.sky b/Cronet/tools/import/copy.bara.sky
index ec274e6..5372a4d 100644
--- a/Cronet/tools/import/copy.bara.sky
+++ b/Cronet/tools/import/copy.bara.sky
@@ -20,6 +20,7 @@
     # Exclude existing *OWNERS files
     "**/*OWNERS",
     "**/.git/**",
+    "**/.gitignore",
 ]
 
 cronet_origin_files = glob(