[SandboxIR] Implement VAArgInst

[vporpo]

This patch implements sandboxir::VAArgInst mirroring llvm::VAArgInst.

[alinas]

LG

[llvm-ci]

LLVM Buildbot has detected a new failure on builder clang-armv8-quick running on linaro-clang-armv8-quick while building llvm at step 5 "ninja check 1".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/154/builds/3403

Here is the relevant piece of the build log for the reference

Step 5 (ninja check 1) failure: stage 1 checked (failure)
******************** TEST 'ClangPseudo :: cxx/dangling-else.cpp' FAILED ********************
Exit Code: 2

Command Output (stderr):
--
RUN: at line 1: clang-pseudo -grammar=cxx -source=/home/tcwg-buildbot/worker/clang-armv8-quick/llvm/clang-tools-extra/pseudo/test/cxx/dangling-else.cpp --start-symbol=statement-seq --print-forest | /home/tcwg-buildbot/worker/clang-armv8-quick/stage1/bin/FileCheck /home/tcwg-buildbot/worker/clang-armv8-quick/llvm/clang-tools-extra/pseudo/test/cxx/dangling-else.cpp
+ /home/tcwg-buildbot/worker/clang-armv8-quick/stage1/bin/FileCheck /home/tcwg-buildbot/worker/clang-armv8-quick/llvm/clang-tools-extra/pseudo/test/cxx/dangling-else.cpp
+ clang-pseudo -grammar=cxx -source=/home/tcwg-buildbot/worker/clang-armv8-quick/llvm/clang-tools-extra/pseudo/test/cxx/dangling-else.cpp --start-symbol=statement-seq --print-forest
clang-pseudo: ../llvm/clang-tools-extra/pseudo/lib/cxx/CXX.cpp:437: auto clang::pseudo::cxx::getLanguage()::(anonymous class)::operator()() const: Assertion `Diags.empty()' failed.
#0 0x0076ed24 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/home/tcwg-buildbot/worker/clang-armv8-quick/stage1/bin/clang-pseudo+0x5ed24)
#1 0x0076cab4 llvm::sys::RunSignalHandlers() (/home/tcwg-buildbot/worker/clang-armv8-quick/stage1/bin/clang-pseudo+0x5cab4)
#2 0x0076f778 SignalHandler(int) Signals.cpp:0:0
#3 0xf7a8d6e0 __default_sa_restorer ./signal/../sysdeps/unix/sysv/linux/arm/sigrestorer.S:67:0
#4 0xf7a7db06 ./csu/../sysdeps/unix/sysv/linux/arm/libc-do-syscall.S:47:0
#5 0xf7abd292 __pthread_kill_implementation ./nptl/pthread_kill.c:44:76
#6 0xf7a8c840 gsignal ./signal/../sysdeps/posix/raise.c:27:6
FileCheck error: '<stdin>' is empty.
FileCheck command line:  /home/tcwg-buildbot/worker/clang-armv8-quick/stage1/bin/FileCheck /home/tcwg-buildbot/worker/clang-armv8-quick/llvm/clang-tools-extra/pseudo/test/cxx/dangling-else.cpp

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[llvm-ci]

LLVM Buildbot has detected a new failure on builder openmp-offload-libc-amdgpu-runtime running on omp-vega20-1 while building llvm at step 6 "test-openmp".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/73/builds/4537

Here is the relevant piece of the build log for the reference

Step 6 (test-openmp) failure: test (failure)
******************** TEST 'libomp :: tasking/issue-94260-2.c' FAILED ********************
Exit Code: -11

Command Output (stdout):
--
# RUN: at line 1
/home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/./bin/clang -fopenmp   -I /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/runtimes/runtimes-bins/openmp/runtime/src -I /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.src/openmp/runtime/test -L /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/runtimes/runtimes-bins/openmp/runtime/src  -fno-omit-frame-pointer -I /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.src/openmp/runtime/test/ompt /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.src/openmp/runtime/test/tasking/issue-94260-2.c -o /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/runtimes/runtimes-bins/openmp/runtime/test/tasking/Output/issue-94260-2.c.tmp -lm -latomic && /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/runtimes/runtimes-bins/openmp/runtime/test/tasking/Output/issue-94260-2.c.tmp
# executed command: /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/./bin/clang -fopenmp -I /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/runtimes/runtimes-bins/openmp/runtime/src -I /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.src/openmp/runtime/test -L /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/runtimes/runtimes-bins/openmp/runtime/src -fno-omit-frame-pointer -I /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.src/openmp/runtime/test/ompt /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.src/openmp/runtime/test/tasking/issue-94260-2.c -o /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/runtimes/runtimes-bins/openmp/runtime/test/tasking/Output/issue-94260-2.c.tmp -lm -latomic
# executed command: /home/ompworker/bbot/openmp-offload-libc-amdgpu-runtime/llvm.build/runtimes/runtimes-bins/openmp/runtime/test/tasking/Output/issue-94260-2.c.tmp
# note: command had no output on stdout or stderr
# error: command failed with exit status: -11

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