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: I0f4e1f044c829332caa4bc79e95ba244bee1aef3
(cherry picked from commit 2c5def62)