In order to validate that the NDK STL paths exists, we need to know
the full path, including the Gcc version during the go execution. So
instead of returning a ninja variable reference, just return the
contents of the variable.
This also fixes a few invalid uses of armGccVersion to the proper
variable.
Change-Id: I54398ba4aa4000235b7d537a2c4efe3ecbbeec8b
34fc3b1e84