Convert libprotobuf to Bazel

Since this is a one-off just for building libprotobuf that will be removed when we handle cargo output more generically (b/297364081), I didn't write a unit test for this CL.

Test: b build //external/rust/crates/protobuf:libprotobuf
Bug: 295925256
Change-Id: I00cf44d54be27a09c184a96c13b250a2e54e2d10
diff --git a/android/allowlists/allowlists.go b/android/allowlists/allowlists.go
index dda125a..7163328 100644
--- a/android/allowlists/allowlists.go
+++ b/android/allowlists/allowlists.go
@@ -513,6 +513,7 @@
 		"libprotobuf_support",
 		"libtinytemplate",
 		"libserde_json",
+		"libprotobuf",
 
 		// ext
 		"tagsoup",