[160053] build Mac MPS with new compiler+linker, and good options
Build different varieties (variety.ci and variety.he) differently.
Upgrade tools from MrC1.0 + PPCLink1.0 to MrC2.0.2d1 + PPCLink1.5.
Drop InterfaceLib from link, because it provokes a PPCLink1.5 error
(Error 3019 while reading file InterfaceLib; File is not an object
file) and is apparently not needed.
The release build (variety.he) is untested -- see .he.untested.
Correct copyright.
Improve build instructions.
Old HE settings are still temporarily available as the pseudo-variety
ZZ, for testing.
Copied from Perforce
Change: 19556
ServerID: perforce.ravenbrook.com
GitHub-reference: https://github.com/Ravenbrook/mps/issues/160053