Compress the binary_size.pb artifact

Bug: 183934389
Test: m out/soong/binary_sizes.pb.gz
Change-Id: Ib79fd9cd82c7029f3ee409df91697797a8be7d06
diff --git a/bloaty/bloaty.go b/bloaty/bloaty.go
index 653c489..764cded 100644
--- a/bloaty/bloaty.go
+++ b/bloaty/bloaty.go
@@ -23,7 +23,7 @@
 )
 
 const bloatyDescriptorExt = ".bloaty.csv"
-const protoFilename = "binary_sizes.pb"
+const protoFilename = "binary_sizes.pb.gz"
 
 var (
 	fileSizeMeasurerKey blueprint.ProviderKey