This is in preparation for the LLVM 4 upgrade (which gets more strict
about e.g., return false in xcbuild itself) and also for using xcbuild
more extensively in the Darwin stdenv bootstrap process, which is why I
killed the unnecessary gcc dependency in the toolchain. llvm-cov pretends
to be gcov anyway, so we're fine.
* All projects are available under NCSA license,
other than dragonegg.
* "Runtime" projects are dual-licensed under
both NCSA and MIT:
libc++, libc++abi, compiler-rt
* I don't mention MIT for compiler-rt as
we only build it as part of LLVM.
It's a long build and generally painful to split into smaller commits,
so I apologize for lumping many changes into one commit but this is far
easier.
There are still several outdated parts of the darwin stdenv but these
changes should bring us closer to the goal.
Fixes#18461
vcunat's review:
- let's not switch the default versions of llvm* for now
- the only changes I see is adding python to clang's buildInputs
and using the big so-file as discussed in #12759
(BUILD_SHARED_LIBS -> LLVM_LINK_LLVM_DYLIB)
- in future it will be nice to split libLLVM into a separate output
