RuleBuilder does its own ninja escaping, so values that will be
passed to RuleBuilder must not be pre-escaped. Add a new
android.ExpandNinjaEscaped method that explicitly handles ninja
escaping. Some of the expansion functions return ninja values
(like "${in}") that need to stay unescaped, so add a bool return
value to the expansion function in android.ExpandNinjaEscaped.
Test: expand_test.go
Change-Id: Ib03d4db38b5e3e5bffbd87acf14f55e276a53d04
An escaped $ sign in an expanded string needs to be re-escaped so it
can pass through to ninja.
Test: m -j libLLVMObject
Change-Id: I2f7890417fd6f534e6e21cace3d86ae9ef708ce5
