crt modules produces cc rules for testing

Previously, crt modules didn't produce cc rules because they didn't have
any input src files set. This prevented us from having a test which
checks the cflags of the crt modules.

Fixing that by adding source file to the crt modules. crtbrand is also
added as an 'objs' dep, because otherwise partialLd rules won't be
generated.

Bug: N/A
Test: m nothing
Change-Id: I731227c20c662c876c40f0c41e1769a271e2c643