Revert "Deduplicate dflags and lflags" (#2016)
Revert "Deduplicate dflags and lflags" (#2016)

PR #2016 introducted a de-duplication strategy that is too eager and corrupts argument chains, such as "-framework CoreServices -framework CoreFoundation" where the "-framework" argument needs to be duplicated for each framework.

This reverts commit 10bea6f07fa460c806cbec56323d600af00d9f09.

Geod24/dub