[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-dylib` running on `linaro-flang-aarch64-dylib` while building `clang,compiler-rt,llvm,runtimes` at step 5 "build-unified-tree".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/50/builds/23612

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

```
Step 5 (build-unified-tree) failure: build (failure)
...
50.268 [96/11/847] Linking CXX static library /home/tcwg-buildbot/worker/flang-aarch64-dylib/build/lib/libruntimes_gtest.a
50.340 [96/10/848] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/matmul-transpose-complex.cpp.o
50.461 [96/9/849] Building Fortran object flang-rt/lib/runtime/CMakeFiles/flang-rt-mod.dir/__cuda_device.f90.o
50.461 [96/8/850] Building Fortran object flang-rt/lib/runtime/CMakeFiles/flang-rt-mod.dir/cuda_runtime_api.f90.o
50.567 [95/8/851] Linking CXX static library /home/tcwg-buildbot/worker/flang-aarch64-dylib/build/lib/libruntimes_gtest_main.a
50.602 [95/7/852] Building Fortran object flang-rt/lib/runtime/CMakeFiles/flang-rt-mod.dir/ieee_exceptions.f90.o
51.131 [95/6/853] Building Fortran object flang-rt/lib/runtime/CMakeFiles/flang-rt-mod.dir/ieee_arithmetic.f90.o
56.984 [95/5/854] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/matmul-complex.cpp.o
62.021 [95/4/855] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/matmul-transpose-extypes-int16.cpp.o
62.211 [94/4/856] Linking CXX shared library openmp/tools/omptest/libomptest.so
FAILED: openmp/tools/omptest/libomptest.so 
: && /home/tcwg-buildbot/worker/flang-aarch64-dylib/build/./bin/clang++ --target=aarch64-unknown-linux-gnu -fPIC -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 -Wall -fcolor-diagnostics -Wcast-qual -Wformat-pedantic -Wimplicit-fallthrough -Wsign-compare -Wno-extra -Wno-pedantic -fno-semantic-interposition -fdata-sections -O3 -DNDEBUG  -Wl,-z,defs -Wl,-z,nodelete -shared -Wl,-soname,libomptest.so -o openmp/tools/omptest/libomptest.so third-party/runtimes_gtest/CMakeFiles/runtimes_gtest.dir/googletest/src/gtest-all.cc.o third-party/runtimes_gtest/CMakeFiles/runtimes_gtest.dir/googlemock/src/gmock-all.cc.o openmp/tools/omptest/CMakeFiles/omptest.dir/src/InternalEvent.cpp.o openmp/tools/omptest/CMakeFiles/omptest.dir/src/InternalEventOperators.cpp.o openmp/tools/omptest/CMakeFiles/omptest.dir/src/Logging.cpp.o openmp/tools/omptest/CMakeFiles/omptest.dir/src/OmptAsserter.cpp.o openmp/tools/omptest/CMakeFiles/omptest.dir/src/OmptAssertEvent.cpp.o openmp/tools/omptest/CMakeFiles/omptest.dir/src/OmptCallbackHandler.cpp.o openmp/tools/omptest/CMakeFiles/omptest.dir/src/OmptTester.cpp.o  /home/tcwg-buildbot/worker/flang-aarch64-dylib/build/lib/libruntimes_gtest.a  -lLLVM && :
/usr/bin/ld: cannot find -lLLVM: No such file or directory
clang++: error: linker command failed with exit code 1 (use -v to see invocation)
62.788 [94/3/857] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/extrema-value.cpp.o
63.599 [94/2/858] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/matmul-transpose-extypes-real16.cpp.o
65.457 [94/1/859] Building CXX object flang-rt/lib/runtime/CMakeFiles/flang_rt.runtime.static.dir/character.cpp.o
ninja: build stopped: subcommand failed.
2286.826 [2/2/7671] Linking CXX executable tools/flang/unittests/Evaluate/intrinsics.test
FAILED: runtimes/runtimes-stamps/runtimes-build /home/tcwg-buildbot/worker/flang-aarch64-dylib/build/runtimes/runtimes-stamps/runtimes-build 
cd /home/tcwg-buildbot/worker/flang-aarch64-dylib/build/runtimes/runtimes-bins && /usr/local/bin/cmake --build .
ninja: build stopped: subcommand failed.

```

</details>

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