[clang] [clang-format] Skip line splices when sorting C++ includes (PR #120680)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-aarch64-sve-vla-2stage` running on `linaro-g3-04` while building `clang` at step 11 "build stage 2".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/41/builds/4282

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

```
Step 11 (build stage 2) failure: 'ninja' (failure)
...
[8332/8795] Building CXX object tools/flang/tools/f18-parse-demo/CMakeFiles/f18-parse-demo.dir/f18-parse-demo.cpp.o
[8333/8795] Linking CXX static library lib/libHLFIRTransforms.a
[8334/8795] Linking CXX executable bin/f18-parse-demo
[8335/8795] Linking CXX executable tools/flang/unittests/Evaluate/logical.test
[8336/8795] Linking CXX executable tools/flang/unittests/Evaluate/real.test
[8337/8795] Linking CXX executable tools/flang/unittests/Evaluate/integer.test
[8338/8795] Linking CXX executable tools/flang/unittests/Evaluate/expression.test
[8339/8795] Linking CXX executable tools/flang/unittests/Evaluate/folding.test
[8340/8795] Linking CXX static library lib/libFortranLower.a
[8341/8795] Building CXX object tools/flang/lib/Frontend/CMakeFiles/flangFrontend.dir/FrontendActions.cpp.o
FAILED: tools/flang/lib/Frontend/CMakeFiles/flangFrontend.dir/FrontendActions.cpp.o 
/home/tcwg-buildbot/worker/clang-aarch64-sve-vla-2stage/stage1.install/bin/clang++ -DFLANG_INCLUDE_TESTS=1 -DFLANG_LITTLE_ENDIAN=1 -DGTEST_HAS_RTTI=0 -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/home/tcwg-buildbot/worker/clang-aarch64-sve-vla-2stage/stage2/tools/flang/lib/Frontend -I/home/tcwg-buildbot/worker/clang-aarch64-sve-vla-2stage/llvm/flang/lib/Frontend -I/home/tcwg-buildbot/worker/clang-aarch64-sve-vla-2stage/llvm/flang/include -I/home/tcwg-buildbot/worker/clang-aarch64-sve-vla-2stage/stage2/tools/flang/include -I/home/tcwg-buildbot/worker/clang-aarch64-sve-vla-2stage/stage2/include -I/home/tcwg-buildbot/worker/clang-aarch64-sve-vla-2stage/llvm/llvm/include -isystem /home/tcwg-buildbot/worker/clang-aarch64-sve-vla-2stage/llvm/llvm/../mlir/include -isystem /home/tcwg-buildbot/worker/clang-aarch64-sve-vla-2stage/stage2/tools/mlir/include -isystem /home/tcwg-buildbot/worker/clang-aarch64-sve-vla-2stage/stage2/tools/clang/include -isystem /home/tcwg-buildbot/worker/clang-aarch64-sve-vla-2stage/llvm/llvm/../clang/include -mcpu=neoverse-512tvb -mllvm -scalable-vectorization=preferred -mllvm -treat-scalable-fixed-error-as-warning=false -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 -Wno-comment -Wstring-conversion -Wmisleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -Wno-deprecated-copy -Wno-string-conversion -Wno-ctad-maybe-unsupported -Wno-unused-command-line-argument -Wstring-conversion           -Wcovered-switch-default -Wno-nested-anon-types -O3 -DNDEBUG -std=c++17  -fno-exceptions -funwind-tables -fno-rtti -UNDEBUG -MD -MT tools/flang/lib/Frontend/CMakeFiles/flangFrontend.dir/FrontendActions.cpp.o -MF tools/flang/lib/Frontend/CMakeFiles/flangFrontend.dir/FrontendActions.cpp.o.d -o tools/flang/lib/Frontend/CMakeFiles/flangFrontend.dir/FrontendActions.cpp.o -c /home/tcwg-buildbot/worker/clang-aarch64-sve-vla-2stage/llvm/flang/lib/Frontend/FrontendActions.cpp
Killed
command timed out: 1200 seconds without output running [b'ninja'], attempting to kill
process killed by signal 9
program finished with exit code -1
elapsedTime=3839.337225

```

</details>

https://github.com/llvm/llvm-project/pull/120680