Switch rsg-generator-support to use no STL, since it is pure C.

We should really fix rsg-generator to install itself, and then be invoked
from a location with access to libc++.so, but this fixes things for the
time being.

Change-Id: Ia019edf7f984b7e0338c1618f3ee207e0899e03e
Merge "Switch rsg-generator-support to use no STL, since it is pure C."