[clang] [compiler-rt] [llvm] Skipping host target exports during cross-compilation (PR #209922)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `flang-aarch64-latest-gcc` running on `linaro-flang-aarch64-latest-gcc` while building `clang,compiler-rt,llvm,runtimes` at step 7 "test-build-unified-tree-check-flang-rt".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/130/builds/20469

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

```
Step 7 (test-build-unified-tree-check-flang-rt) failure: test (failure)
...
-- Configuring done (2.1s)
-- Generating done (0.3s)
-- Build files have been written to: /home/tcwg-buildbot/worker/flang-aarch64-latest-gcc/build/runtimes/runtimes-bins
5.609 [0/1/4] cd /home/tcwg-buildbot/worker/flang-aarch64-latest-gcc/build/runtimes/runtimes-bins && /usr/bin/cmake --build /home/tcwg-buildbot/worker/flang-aarch64-latest-gcc/build/runtimes/runtimes-bins/ --target check-flang-rt --config Release
2.777 [40/5/1] Building CXX object flang-rt/lib/Testing/CMakeFiles/NonGTestTesting.dir/home/tcwg-buildbot/worker/flang-aarch64-latest-gcc/llvm-project/flang/lib/Testing/fp-testing.cpp.o
3.211 [40/4/2] Building CXX object flang-rt/lib/Testing/CMakeFiles/NonGTestTesting.dir/home/tcwg-buildbot/worker/flang-aarch64-latest-gcc/llvm-project/flang/lib/Testing/testing.cpp.o
3.344 [37/6/3] Linking CXX static library flang-rt/lib/Testing/libNonGTestTesting.a
3.644 [37/5/4] Building CXX object flang-rt/unittests/Evaluate/CMakeFiles/reshape.test.dir/reshape.cpp.o
3.658 [35/6/5] Building CXX object flang-rt/unittests/Evaluate/CMakeFiles/ISO-Fortran-binding.test.dir/ISO-Fortran-binding.cpp.o
4.165 [32/8/6] Linking CXX executable flang-rt/unittests/Evaluate/ISO-Fortran-binding.test
FAILED: flang-rt/unittests/Evaluate/ISO-Fortran-binding.test 
: && /home/tcwg-buildbot/worker/flang-aarch64-latest-gcc/build/./bin/clang++ --target=aarch64-unknown-linux-gnu -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 -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 -O3 -DNDEBUG  flang-rt/unittests/Evaluate/CMakeFiles/ISO-Fortran-binding.test.dir/ISO-Fortran-binding.cpp.o -o flang-rt/unittests/Evaluate/ISO-Fortran-binding.test  flang-rt/lib/Testing/libNonGTestTesting.a  /home/tcwg-buildbot/worker/flang-aarch64-latest-gcc/build/lib/clang/24/lib/aarch64-unknown-linux-gnu/libflang_rt.runtime.a  -lLLVMSupport && :
/usr/bin/ld: cannot find -lLLVMSupport: No such file or directory
clang++: error: linker command failed with exit code 1 (use -v to see invocation)
4.191 [32/7/7] Linking CXX executable flang-rt/unittests/Evaluate/reshape.test
FAILED: flang-rt/unittests/Evaluate/reshape.test 
: && /home/tcwg-buildbot/worker/flang-aarch64-latest-gcc/build/./bin/clang++ --target=aarch64-unknown-linux-gnu -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 -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 -O3 -DNDEBUG  flang-rt/unittests/Evaluate/CMakeFiles/reshape.test.dir/reshape.cpp.o -o flang-rt/unittests/Evaluate/reshape.test  flang-rt/lib/Testing/libNonGTestTesting.a  /home/tcwg-buildbot/worker/flang-aarch64-latest-gcc/build/lib/clang/24/lib/aarch64-unknown-linux-gnu/libflang_rt.runtime.a  -lLLVMSupport && :
/usr/bin/ld: cannot find -lLLVMSupport: No such file or directory
clang++: error: linker command failed with exit code 1 (use -v to see invocation)
6.999 [32/6/8] Building CXX object flang-rt/unittests/Runtime/CMakeFiles/RuntimeTests.dir/AccessTest.cpp.o
8.427 [32/5/9] Building CXX object flang-rt/unittests/Runtime/CMakeFiles/RuntimeTests.dir/BufferTest.cpp.o
8.748 [32/4/10] Building CXX object flang-rt/unittests/Runtime/CMakeFiles/RuntimeTests.dir/Allocatable.cpp.o
9.657 [32/3/11] Building CXX object flang-rt/unittests/Runtime/CMakeFiles/RuntimeTests.dir/ArrayConstructor.cpp.o
9.706 [32/2/12] Building CXX object flang-rt/unittests/Runtime/CMakeFiles/RuntimeTests.dir/Assign.cpp.o
19.788 [32/1/13] Building CXX object flang-rt/unittests/Runtime/CMakeFiles/RuntimeTests.dir/CharacterTest.cpp.o
ninja: build stopped: subcommand failed.
FAILED: runtimes/CMakeFiles/check-flang-rt /home/tcwg-buildbot/worker/flang-aarch64-latest-gcc/build/runtimes/CMakeFiles/check-flang-rt 
cd /home/tcwg-buildbot/worker/flang-aarch64-latest-gcc/build/runtimes/runtimes-bins && /usr/bin/cmake --build /home/tcwg-buildbot/worker/flang-aarch64-latest-gcc/build/runtimes/runtimes-bins/ --target check-flang-rt --config Release
ninja: build stopped: subcommand failed.

```

</details>

https://github.com/llvm/llvm-project/pull/209922