Rename variables with "-" in androidmk

Make variables containg a "-" would succeed the translation to
blueprint, only to fail during the blueprint format step. Rename those
variables with a "-" and update references to them.

Test: androidmk_test.go
Bug: 112653593
Change-Id: Ifcbe1c6749a1e7f1e0b78cd6f01a8f1f52a334d0