Log message:
Update buildlink3.mk with reality in LLVM projects

Log message:
LLVM 4.0.0:
The minimum compiler version required for building LLVM has been raised to 4.8 \ 
for GCC and 2015 for Visual Studio.
The C API functions LLVMAddFunctionAttr, LLVMGetFunctionAttr, \ 
LLVMRemoveFunctionAttr, LLVMAddAttribute, LLVMRemoveAttribute, LLVMGetAttribute, \ 
LLVMAddInstrAttribute and LLVMRemoveInstrAttribute have been removed.
The C API enum LLVMAttribute has been deleted.
The definition and uses of LLVM_ATRIBUTE_UNUSED_RESULT in the LLVM source were \ 
replaced with LLVM_NODISCARD, which matches the C++17 [[nodiscard]] semantics \ 
rather than gcc’s __attribute__((warn_unused_result)).
The Timer related APIs now expect a Name and Description. When upgrading code \ 
the previously used names should become descriptions and a short name in the \ 
style of a programming language identifier should be added.
LLVM now handles invariant.group across different basic blocks, which makes it \ 
possible to devirtualize virtual calls inside loops.
The aggressive dead code elimination phase (“adce”) now removes \ 
branches which do not effect program behavior. Loops are retained by default \ 
since they may be infinite but these can also be removed with LLVM option \ 
-adce-remove-loops when the loop body otherwise has no live operations.
The llvm-cov tool can now export coverage data as json. Its html output mode has \ 
also improved.

Log message:
Changes 3.9.1:
The LLVMContext gains a new runtime check (see LLVMContext::discardValueNames()) \ 
that can be set to discard Value names (other than GlobalValue). This is \ 
intended to be used in release builds by clients that are interested in saving \ 
CPU/memory as much as possible.
There is no longer a “global context” available in LLVM, except for \ 
the C API.
The autoconf build system has been removed in favor of CMake. LLVM 3.9 requires \ 
CMake 3.4.3 or later to build. For information about using CMake please see the \ 
documentation on Building LLVM with CMake. For information about the CMake \ 
language there is also a CMake Primer document available.
C API functions LLVMParseBitcode, LLVMParseBitcodeInContext, \ 
LLVMGetBitcodeModuleInContext and LLVMGetBitcodeModule having been removed. \ 
LLVMGetTargetMachineData has been removed (use LLVMGetDataLayout instead).
The C API function LLVMLinkModules has been removed.
The C API function LLVMAddTargetData has been removed.
The C API function LLVMGetDataLayout is deprecated in favor of LLVMGetDataLayoutStr.
The C API enum LLVMAttribute and associated API is deprecated in favor of the \ 
new LLVMAttributeRef API. The deprecated functions are LLVMAddFunctionAttr, \ 
LLVMAddTargetDependentFunctionAttr, LLVMRemoveFunctionAttr, LLVMGetFunctionAttr, \ 
LLVMAddAttribute, LLVMRemoveAttribute, LLVMGetAttribute, LLVMAddInstrAttribute, \ 
LLVMRemoveInstrAttribute and LLVMSetInstrParamAlignment.
TargetFrameLowering::eliminateCallFramePseudoInstr now returns an iterator to \ 
the next instruction instead of void. Targets that previously did MBB.erase(I); \ 
return; now probably want return MBB.erase(I);.
SelectionDAGISel::Select now returns void. Out-of-tree targets will need to be \ 
updated to replace the argument node and remove any dead nodes in cases where \ 
they currently return an SDNode * from this interface.
Added the MemorySSA analysis, which hopes to replace MemoryDependenceAnalysis. \ 
It should provide higher-quality results than MemDep, and be algorithmically \ 
faster than MemDep. Currently, GVNHoist (which is off by default) makes use of \ 
MemorySSA.
The minimum density for lowering switches with jump tables has been reduced from \ 
40% to 10% for functions which are not marked optsize (that is, compiled with \ 
-Os).

Log message:
Update llvm packages to 3.9.0

* Drop CppBackend. It is removed.

Changelog:
* GCC ABI Tag
* LLVM IR: new intrinsics etc.
* Change LLVM IPO model
* Support ThinLTO
* Improve the ARM targets, ARMv8.2-A support etc.
* Improve the MIPS targets
* Improve the PowerPC target, default optim O3 to O2
* Improve the X86 target, SKylake AVX-512 etc.
* Improve the AMDGPU, better support for Mesa 12

Log message:
Updated libunwind to 3.8.1.

Another part of llvm-3.8.1.

Log message:
Import libunwind-3.8.0 as lang/libunwind

LLVM libunwind

Late import approved from <pkgsrc-pmc>