Disable vendor path check for mainline variants

This matches what is done for mainline_system_arm64
(in this particular branch).

Test: lunch mainline_system_x86 && m nothing
Change-Id: I4eb236d086bd36b4821ed11411fa404f2d45f2b9
Merged-In: I607781ce7c6299cbc98c54c683d04db3b65c2e21