Recognize some unsupported functions

Some functions are called without the use of $(call),
since $(call) is not necessary when the function doesn't
take any arguments. mk2rbc thinks these function calls
are local variables, and converts them as such. This
leads to undefined variable errors when trying to load
(before even executing) the starlark file.

Hardcode a known function that should not be converted
to a local variable.

Bug: 226974242
Test: go test
Change-Id: I5567a34fcc282b181a7e78ac3d5cc9b40bd025a2