Upstream bug: https://bugs.llvm.org/show_bug.cgi?id=33528

When trying to Build LLVM using the following cmake options:

cmake -G Ninja -DCMAKE_INSTALL_PREFIX=/usr -DLLVM_LIBDIR_SUFFIX=64 -DLLVM_BUILD_LLVM_DYLIB=ON -DLLVM_LINK_LLVM_DYLIB=ON -DLLVM_ENABLE_TIMESTAMPS=OFF -DLLVM_TARGETS_TO_BUILD=all -DLLVM_BUILD_TESTS=no -DLLVM_ENABLE_FFI=yes -DLLVM_ENABLE_TERMINFO=yes -DLLVM_ENABLE_ASSERTIONS=yes -DLLVM_ENABLE_EH=ON -DLLVM_ENABLE_RTTI=ON -DWITH_POLLY=OFF -DLLVM_HOST_TRIPLE=x86_64-pc-linux-gnu -DFFI_INCLUDE_DIR=/usr/lib64/libffi-3.1/include  -DFFI_LIBRARY_DIR= -DLLVM_BINUTILS_INCDIR=/usr/include -DHAVE_HISTEDIT_H=no -DENABLE_LINKER_BUILD_ID=ON -DCLANG_VENDOR=Chromium -DCLANG_DEFAULT_CXX_STDLIB= -DCLANG_DEFAULT_RTLIB= -DOCAMLFIND=NO -DGO_EXECUTABLE=GO_EXECUTABLE-NOTFOUND -DLLVM_BUILD_DOCS=no -DLLVM_ENABLE_SPHINX=no -DLLVM_ENABLE_DOXYGEN=OFF -DLLVM_INSTALL_HTML=/usr/share/doc/llvm-5.0_pre300080-r10/html -DSPHINX_WARNINGS_AS_ERRORS=OFF -DLLVM_INSTALL_UTILS=ON -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_DO_STRIP=OFF  llvm_source_dir

CMake errors out:

CMake Error in cmake/modules/CMakeLists.txt:
  export called with target "LLVMTestingSupport" which requires target
  "gtest" that is not in the export set.

  If the required target is not easy to reference in this call, consider
  using the APPEND option with multiple separate calls.