Fix environment for protobuf compilation (#23664)

Add use_default_shell_env = True to protoc invocation to mirror
what the protobuf cc_proto_library & co are doing
Fixes a failure in invocing protoc when it is build in a non-default
environment (e.g. with a custom LD_LIBRARY_PATH)

bazel/generate_cc.bzl

@@ -154,6 +154,7 @@ def generate_cc_impl(ctx):
         outputs = out_files,
         executable = ctx.executable._protoc,
         arguments = arguments,
+        use_default_shell_env = True,
     )
 
     return struct(files = depset(out_files))