ModuleInterface: properly handle equal-joined arguments in the ignorable flags field
ModuleInterface: properly handle equal-joined arguments in the ignorable flags field

Previously, we have an assumption that all equal-joined arguments are alias to the
separate forms, e.g. -tbd-install_name=Foo is an alias to -tbd-install_name Foo. However,
it seems having only the equal-joined version of an argument is possible. This PR adds
support to that scenario.

atrick/swift,gregomni/swift,JGiola/swift,benlangmuir/swift,gregomni/swift,apple/swift,JGiola/swift,roambotics/swift,ahoppen/swift,atrick/swift,gregomni/swift,apple/swift,roambotics/swift,JGiola/swift,JGiola/swift,rudkx/swift,glessard/swift,ahoppen/swift,gregomni/swift,benlangmuir/swift,rudkx/swift,benlangmuir/swift,ahoppen/swift,glessard/swift,roambotics/swift,JGiola/swift,rudkx/swift,roambotics/swift,glessard/swift,roambotics/swift,ahoppen/swift,ahoppen/swift,glessard/swift,roambotics/swift,apple/swift,rudkx/swift,glessard/swift,ahoppen/swift,JGiola/swift,rudkx/swift,rudkx/swift,apple/swift,benlangmuir/swift,atrick/swift,atrick/swift,gregomni/swift,glessard/swift,benlangmuir/swift,atrick/swift,apple/swift,apple/swift,benlangmuir/swift,gregomni/swift,atrick/swift