Decouple the package from lang/clang that so it can be maintained
and updated independently.
This switches the build framework from autoconf to cmake.
There are no significant changes to the AMDGPU target mentioned in
the release notes. Other changes are not relevant to mention here since
mesa is the only user of this package in pkgsrc proper.
Compacted version of upstream's release notes:
The LLVM C API LLVMGetTargetMachineData is deprecated
DataLayout is no longer optional
Comdats are now ortogonal to the linkage
On ELF now supports multiple sections with the same name and comdat
LLVM now lazily loads metadata in some cases
Creating archives with IR files with debug info is now 25X faster
llvm-ar(1) can create archives in the BSD format used by OS X
LLVM received a backend for the extended Berkely Packet Filter instruction set
The BPF target is now available by default
Switch-case lowering was rewritten to avoid generating unbalanced search trees
The debug info IR class hierarchy now inherits from Metadata
Argument-less TargetMachine::getSubtarget has been removed from the tree
