[llvm] IR: Introduce "thread-model" module flag (PR #222768)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `ppc64le-mlir-rhel-clang` running on `ppc64le-mlir-rhel-test` while building `llvm` at step 5 "build-check-mlir-build-only".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/129/builds/52552

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

```
Step 5 (build-check-mlir-build-only) failure: build (failure)
...
108.990 [3251/14/1596] Linking CXX static library lib/libMLIRQueryMatcher.a
109.014 [3251/13/1597] Linking CXX static library lib/libMLIRLoopLikeInterface.a
109.027 [3251/12/1598] Linking CXX executable tools/mlir/unittests/Dialect/Utils/MLIRDialectUtilsTests
109.043 [3251/11/1599] Linking CXX executable tools/mlir/unittests/Dialect/MLIRDialectTests
109.100 [3251/10/1600] Linking CXX static library lib/libMLIRTranslateLib.a
109.602 [3251/9/1601] Linking CXX static library lib/libMLIRLspServerLib.a
109.602 [3251/8/1602] Linking CXX executable tools/mlir/unittests/Debug/MLIRDebugTests
109.651 [3251/7/1603] Linking CXX executable tools/mlir/unittests/Bytecode/MLIRBytecodeTests
114.997 [3251/6/1604] Building MPITypes.h.inc...
117.318 [3251/5/1605] Building CXX object tools/mlir/lib/Rewrite/CMakeFiles/obj.MLIRRewrite.dir/FrozenRewritePatternSet.cpp.o
FAILED: tools/mlir/lib/Rewrite/CMakeFiles/obj.MLIRRewrite.dir/FrozenRewritePatternSet.cpp.o 
ccache /home/buildbots/llvm-external-buildbots/clang.19.1.7/bin/clang++ -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GLIBCXX_USE_CXX11_ABI=1 -D_GNU_SOURCE -D_LIBCPP_HARDENING_MODE=_LIBCPP_HARDENING_MODE_EXTENSIVE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-mlir-rhel-test/ppc64le-mlir-rhel-clang-build/build/tools/mlir/lib/Rewrite -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-mlir-rhel-test/ppc64le-mlir-rhel-clang-build/llvm-project/mlir/lib/Rewrite -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-mlir-rhel-test/ppc64le-mlir-rhel-clang-build/build/tools/mlir/include -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-mlir-rhel-test/ppc64le-mlir-rhel-clang-build/llvm-project/mlir/include -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-mlir-rhel-test/ppc64le-mlir-rhel-clang-build/build/include -I/home/buildbots/llvm-external-buildbots/workers/ppc64le-mlir-rhel-test/ppc64le-mlir-rhel-clang-build/llvm-project/llvm/include -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -pedantic -Wno-long-long -Wc++98-compat-extra-semi -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wno-pass-failed -Wmisleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -Xclang -fno-pch-timestamp -Wundef -Werror=mismatched-tags -Werror=global-constructors -O3 -DNDEBUG -std=c++17 -UNDEBUG -fno-exceptions -funwind-tables -fno-rtti -Winvalid-pch -Xclang -include-pch -Xclang /home/buildbots/llvm-external-buildbots/workers/ppc64le-mlir-rhel-test/ppc64le-mlir-rhel-clang-build/build/tools/mlir/lib/IR/CMakeFiles/obj.MLIRIR.dir/cmake_pch.hxx.pch -Xclang -include -Xclang /home/buildbots/llvm-external-buildbots/workers/ppc64le-mlir-rhel-test/ppc64le-mlir-rhel-clang-build/build/tools/mlir/lib/IR/CMakeFiles/obj.MLIRIR.dir/cmake_pch.hxx -MD -MT tools/mlir/lib/Rewrite/CMakeFiles/obj.MLIRRewrite.dir/FrozenRewritePatternSet.cpp.o -MF tools/mlir/lib/Rewrite/CMakeFiles/obj.MLIRRewrite.dir/FrozenRewritePatternSet.cpp.o.d -o tools/mlir/lib/Rewrite/CMakeFiles/obj.MLIRRewrite.dir/FrozenRewritePatternSet.cpp.o -c /home/buildbots/llvm-external-buildbots/workers/ppc64le-mlir-rhel-test/ppc64le-mlir-rhel-clang-build/llvm-project/mlir/lib/Rewrite/FrozenRewritePatternSet.cpp
In file included from /home/buildbots/llvm-external-buildbots/workers/ppc64le-mlir-rhel-test/ppc64le-mlir-rhel-clang-build/llvm-project/mlir/lib/Rewrite/FrozenRewritePatternSet.cpp:21:
/home/buildbots/llvm-external-buildbots/workers/ppc64le-mlir-rhel-test/ppc64le-mlir-rhel-clang-build/llvm-project/mlir/include/mlir/Dialect/PDLInterp/IR/PDLInterp.h:36:10: fatal error: 'mlir/Dialect/PDLInterp/IR/PDLInterpOps.h.inc' file not found
   36 | #include "mlir/Dialect/PDLInterp/IR/PDLInterpOps.h.inc"
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.
118.332 [3251/4/1606] Building PDLInterpOps.h.inc...
125.836 [3251/3/1607] Building MPIOps.h.inc...
131.030 [3251/2/1608] Building MPITypes.cpp.inc...
134.292 [3251/1/1609] Building AMDGPUTargetParserDef.inc...
ninja: build stopped: subcommand failed.

```

</details>

https://github.com/llvm/llvm-project/pull/222768