update build infrastructure for llvm-16.0.6

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 10.0.1.

Update build infrastructure for LLVM 10.0.0.

ok hackroom@
tested by plenty

Update clang build infrastructure for LLVM 8.0.0.

Build and install a shared libLLVM, llvm-config and llvm includes.
This is required to build the radeonsi Mesa driver.

ok patrick@

In preparation for reusing libLLVM component library Makefiles to build
libLLVM from a single directory avoid reused filenames by symlinking
duplicated names with a prefix of the component library na

In preparation for reusing libLLVM component library Makefiles to build
libLLVM from a single directory avoid reused filenames by symlinking
duplicated names with a prefix of the component library name so object
file names will be unique.

symlink approach suggested by deraadt@ ok patrick@

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Update clang build infrastructure for LLVM 7.0.1.

Refactor retguard to make adding additional arches easier.

Add RETGUARD to clang for amd64. This security mechanism uses per-function
random cookies to protect access to function return instructions, with the
effect that the integrity of the return address i

Add RETGUARD to clang for amd64. This security mechanism uses per-function
random cookies to protect access to function return instructions, with the
effect that the integrity of the return address is protected, and function
return instructions are harder to use in ROP gadgets.

On function entry the return address is combined with a per-function random
cookie and stored in the stack frame. The integrity of this value is verified
before function return, and if this check fails, the program aborts. In this way
RETGUARD is an improved stack protector, since the cookies are per-function. The
verification routine is constructed such that the binary space immediately
before each ret instruction is padded with int03 instructions, which makes these
return instructions difficult to use in ROP gadgets. In the kernel, this has the
effect of removing approximately 50% of total ROP gadgets, and 15% of unique
ROP gadgets compared to the 6.3 release kernel. Function epilogues are
essentially gadget free, leaving only the polymorphic gadgets that result from
jumping into the instruction stream partway through other instructions. Work to
remove these gadgets will continue through other mechanisms.

Remaining work includes adding this mechanism to assembly routines, which must
be done by hand. Many thanks to all those who helped test and provide feedback,
especially deaadt, tb, espie and naddy.

ok deraadt@

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Update clang build infrastructure for LLVM 6.0.0.

Update clang build infrastructure for LLVM 5.0.0.

zap empty depends/silence empty installs.
okay millert@

Update clang build infrastructure for LLVM 4.0.0

Discussed with kettenis@

Update clang build infrastructure for LLVM 3.9.1

"go ahead" kettenis@
"just go ahead" deraadt@
"sounds good to me" stefan@

LLVM/Clang build system. This only builds the bare minimum of what is needed
to get a working "clang" binary.

Note that you need GCC from ports to bootstrap clang.

looks good to patrick@, ok jsg@

LLVM/Clang build system. This only builds the bare minimum of what is needed
to get a working "clang" binary.

Note that you need GCC from ports to bootstrap clang.

looks good to patrick@, ok jsg@ kettenis@

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