[clang] [Serialization] Fix crash while lazy-loading template specializations (PR #150430)

[Sam Clegg via cfe-commits]

sbc100 wrote:

This new test as been failing on the emscripten-releases waterfall since it landed.  I'm not sure how or why.  See https://ci.chromium.org/ui/p/emscripten-releases/builders/ci/linux-test-suites/b8707729317947832529/overview

```
@@@BUILD_STEP LLVM regression tests@@@
subprocess.check_call(`ninja check-all`, cwd=`/b/s/w/ir/cache/builder/emscripten-releases/build/llvm-out`)
[1/3] Preparing lit tests
[2/3] cd /b/s/w/ir/cache/builder/emscripten-releases/llvm-project/clang/bindings/python && /b/s/w/ir/cache/builder/emscripten-releases/cmake-3.21.3-linux-x86_64/bin/cmake -E env CLANG_NO_DEFAULT_CONFIG=1 CLANG_LIBRARY_PATH=/b/s/w/ir/cache/builder/emscripten-releases/build/llvm-out/lib /home/chrome-bot/.cache/vpython-root.1000/store/python_venv-bv3d5jfr6u91rvk3n0abpuif20/contents/bin/python3 -m unittest discover
.....................................................................................................................................................................
----------------------------------------------------------------------
Ran 165 tests in 0.753s

OK
[2/3] Running all regression tests
llvm-lit: /b/s/w/ir/cache/builder/emscripten-releases/llvm-project/llvm/utils/lit/lit/llvm/config.py:520: note: using split-file: /b/s/w/ir/cache/builder/emscripten-releases/build/llvm-out/bin/split-file
llvm-lit: /b/s/w/ir/cache/builder/emscripten-releases/llvm-project/llvm/utils/lit/lit/llvm/config.py:520: note: using yaml2obj: /b/s/w/ir/cache/builder/emscripten-releases/build/llvm-out/bin/yaml2obj
llvm-lit: /b/s/w/ir/cache/builder/emscripten-releases/llvm-project/llvm/utils/lit/lit/llvm/config.py:520: note: using llvm-objcopy: /b/s/w/ir/cache/builder/emscripten-releases/build/llvm-out/bin/llvm-objcopy
llvm-lit: /b/s/w/ir/cache/builder/emscripten-releases/llvm-project/llvm/utils/lit/lit/llvm/config.py:520: note: using ld.lld: /b/s/w/ir/cache/builder/emscripten-releases/build/llvm-out/bin/ld.lld
llvm-lit: /b/s/w/ir/cache/builder/emscripten-releases/llvm-project/llvm/utils/lit/lit/llvm/config.py:520: note: using lld-link: /b/s/w/ir/cache/builder/emscripten-releases/build/llvm-out/bin/lld-link
llvm-lit: /b/s/w/ir/cache/builder/emscripten-releases/llvm-project/llvm/utils/lit/lit/llvm/config.py:520: note: using ld64.lld: /b/s/w/ir/cache/builder/emscripten-releases/build/llvm-out/bin/ld64.lld
llvm-lit: /b/s/w/ir/cache/builder/emscripten-releases/llvm-project/llvm/utils/lit/lit/llvm/config.py:520: note: using wasm-ld: /b/s/w/ir/cache/builder/emscripten-releases/build/llvm-out/bin/wasm-ld
llvm-lit: /b/s/w/ir/cache/builder/emscripten-releases/llvm-project/llvm/utils/lit/lit/llvm/config.py:520: note: using clang: /b/s/w/ir/cache/builder/emscripten-releases/build/llvm-out/bin/clang
llvm-lit: /b/s/w/ir/cache/builder/emscripten-releases/llvm-project/llvm/utils/lit/lit/llvm/subst.py:126: note: Did not find cir-opt in /b/s/w/ir/cache/builder/emscripten-releases/build/llvm-out/bin:/b/s/w/ir/cache/builder/emscripten-releases/build/llvm-out/bin
llvm-lit: /b/s/w/ir/cache/builder/emscripten-releases/llvm-project/llvm/utils/lit/lit/llvm/subst.py:126: note: Did not find clang-repl in /b/s/w/ir/cache/builder/emscripten-releases/build/llvm-out/bin:/b/s/w/ir/cache/builder/emscripten-releases/build/llvm-out/bin
llvm-lit: /b/s/w/ir/cache/builder/emscripten-releases/llvm-project/llvm/utils/lit/lit/llvm/config.py:520: note: using ld.lld: /b/s/w/ir/cache/builder/emscripten-releases/build/llvm-out/bin/ld.lld
llvm-lit: /b/s/w/ir/cache/builder/emscripten-releases/llvm-project/llvm/utils/lit/lit/llvm/config.py:520: note: using lld-link: /b/s/w/ir/cache/builder/emscripten-releases/build/llvm-out/bin/lld-link
llvm-lit: /b/s/w/ir/cache/builder/emscripten-releases/llvm-project/llvm/utils/lit/lit/llvm/config.py:520: note: using ld64.lld: /b/s/w/ir/cache/builder/emscripten-releases/build/llvm-out/bin/ld64.lld
llvm-lit: /b/s/w/ir/cache/builder/emscripten-releases/llvm-project/llvm/utils/lit/lit/llvm/config.py:520: note: using wasm-ld: /b/s/w/ir/cache/builder/emscripten-releases/build/llvm-out/bin/wasm-ld
llvm-lit: /b/s/w/ir/cache/builder/emscripten-releases/build/llvm-out/utils/lit/tests/lit.cfg:111: warning: Setting a timeout per test not supported. Requires the Python psutil module but it could not be found. Try installing it via pip or via your operating system's package manager.
 Some tests will be skipped and the --timeout command line argument will not work.
llvm-lit: /b/s/w/ir/cache/builder/emscripten-releases/llvm-project/llvm/utils/lit/lit/llvm/config.py:520: note: using ld.lld: /b/s/w/ir/cache/builder/emscripten-releases/build/llvm-out/bin/ld.lld
llvm-lit: /b/s/w/ir/cache/builder/emscripten-releases/llvm-project/llvm/utils/lit/lit/llvm/config.py:520: note: using lld-link: /b/s/w/ir/cache/builder/emscripten-releases/build/llvm-out/bin/lld-link
llvm-lit: /b/s/w/ir/cache/builder/emscripten-releases/llvm-project/llvm/utils/lit/lit/llvm/config.py:520: note: using ld64.lld: /b/s/w/ir/cache/builder/emscripten-releases/build/llvm-out/bin/ld64.lld
llvm-lit: /b/s/w/ir/cache/builder/emscripten-releases/llvm-project/llvm/utils/lit/lit/llvm/config.py:520: note: using wasm-ld: /b/s/w/ir/cache/builder/emscripten-releases/build/llvm-out/bin/wasm-ld
-- Testing: 83573 tests, 8 workers --
Testing: 
 0
..
 
10
.

FAIL: Clang :: Modules/specializations-lazy-load-parentmap-crash.cpp (14819 of 83573)
******************** TEST 'Clang :: Modules/specializations-lazy-load-parentmap-crash.cpp' FAILED ********************
```

https://github.com/llvm/llvm-project/pull/150430