[compiler-rt] [llvm] [asan] Fix misalignment of variables in fake stack frames (PR #152819)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-clang-x86_64-gcc-ubuntu-no-asserts` running on `doug-worker-6` while building `compiler-rt` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/202/builds/2807

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'AddressSanitizer-x86_64-linux-dynamic :: TestCases/fakestack_alignment.cpp' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
/home/buildbot/buildbot-root/gcc-no-asserts/build/./bin/clang  --driver-mode=g++ -fsanitize=address -mno-omit-leaf-frame-pointer -fno-omit-frame-pointer -fno-optimize-sibling-calls -gline-tables-only  -m64  -shared-libasan -fsanitize-address-use-after-return=always -O0 -DALIGNMENT=4096  -DTHREAD_COUNT=1 -DTHREAD_STACK_SIZE=65536 /home/buildbot/buildbot-root/gcc-no-asserts/llvm-project/compiler-rt/test/asan/TestCases/fakestack_alignment.cpp -o /home/buildbot/buildbot-root/gcc-no-asserts/build/runtimes/runtimes-bins/compiler-rt/test/asan/X86_64LinuxDynamicConfig/TestCases/Output/fakestack_alignment.cpp.tmp &&  /home/buildbot/buildbot-root/gcc-no-asserts/build/runtimes/runtimes-bins/compiler-rt/test/asan/X86_64LinuxDynamicConfig/TestCases/Output/fakestack_alignment.cpp.tmp 2>&1 # RUN: at line 4
+ /home/buildbot/buildbot-root/gcc-no-asserts/build/./bin/clang --driver-mode=g++ -fsanitize=address -mno-omit-leaf-frame-pointer -fno-omit-frame-pointer -fno-optimize-sibling-calls -gline-tables-only -m64 -shared-libasan -fsanitize-address-use-after-return=always -O0 -DALIGNMENT=4096 -DTHREAD_COUNT=1 -DTHREAD_STACK_SIZE=65536 /home/buildbot/buildbot-root/gcc-no-asserts/llvm-project/compiler-rt/test/asan/TestCases/fakestack_alignment.cpp -o /home/buildbot/buildbot-root/gcc-no-asserts/build/runtimes/runtimes-bins/compiler-rt/test/asan/X86_64LinuxDynamicConfig/TestCases/Output/fakestack_alignment.cpp.tmp
/usr/bin/ld: /tmp/lit-tmp-vofnfi6v/fakestack_alignment-1c2aa0.o: undefined reference to symbol 'pthread_attr_setstacksize@@GLIBC_2.2.5'
/usr/bin/ld: /lib/x86_64-linux-gnu/libpthread.so.0: error adding symbols: DSO missing from command line
clang: error: linker command failed with exit code 1 (use -v to see invocation)

--

********************


```

</details>

https://github.com/llvm/llvm-project/pull/152819