[Vendor] When an explicit BS file exists in lib root, use that.
[Vendor] When an explicit BS file exists in lib root, use that.

This allows a lib author to override the BS metadata by (manually)
creating and supplying one, which seems to be the case with Joybox.

beni55/RubyMotion,jjaffeux/RubyMotion,katsuyoshi/RubyMotion,incbee/RubyMotion,incbee/RubyMotion,jjaffeux/RubyMotion,katsuyoshi/RubyMotion,hboon/RubyMotion,HipByte/RubyMotion,hboon/RubyMotion,jjaffeux/RubyMotion,katsuyoshi/RubyMotion,beni55/RubyMotion,HipByte/RubyMotion,hboon/RubyMotion,jjaffeux/RubyMotion,beni55/RubyMotion,katsuyoshi/RubyMotion,HipByte/RubyMotion,incbee/RubyMotion,beni55/RubyMotion,incbee/RubyMotion