set .NOTPARALLEL for AMDGPU tblgen files to tame memory usage on i386ok deraadt@
Update build infrastructure for LLVM 13.0.0.
Update clang build infrastructure for LLVM 11.1.0.Heavy lifting by mortimer@, thank you so much!
Update build infrastructure for LLVM 10.0.0.ok hackroom@tested by plenty
add Makefiles for AMDGPU targetok patrick@