We can use use `stdenv.hostPlatform.isStatic` instead, and move the
logic per package. The least opionated benefit of this is that it makes
it much easier to replace packages with modified ones, as there is no
longer any issue of overlay order.
CC @FRidh @matthewbauer
* starting with rc2
* make `lldb` compilable again on Darwin
* separate out manpage creation for `lldb` into a new derivation
* minor tweaks to the patching of sources,
some of which are backportable to earlier versions