UnitTestVariantArrayHandle routinely breaks

Using g++ 7.5.0 on a (beefy) Ubuntu 18.04 desktop, I break the compiler using ninja:

vtkm/build$ ninja
[72/98] Building CXX object vtkm/cont/testing/CMakeFiles/UnitTests_vtkm_cont_testing.dir/UnitTestVariantArrayHandle.cxx.o
FAILED: vtkm/cont/testing/CMakeFiles/UnitTests_vtkm_cont_testing.dir/UnitTestVariantArrayHandle.cxx.o 
/usr/bin/c++  -DVTKM_NO_ERROR_ON_MIXED_CUDA_CXX_TAG -I../ -Iinclude -I../vtkm/thirdparty/optionparser -I../vtkm/thirdparty/diy -I../vtkm/thirdparty/lcl/vtkmlcl -fno-omit-frame-pointer -O2 -g -DNDEBUG -fPIE -fvisibility=hidden   -Wall -Wcast-align -Wchar-subscripts -Wextra -Wpointer-arith -Wformat -Wformat-security -Wshadow -Wunused -fno-common -Wfloat-conversion -Wodr -ffunction-sections -pthread -MD -MT vtkm/cont/testing/CMakeFiles/UnitTests_vtkm_cont_testing.dir/UnitTestVariantArrayHandle.cxx.o -MF vtkm/cont/testing/CMakeFiles/UnitTests_vtkm_cont_testing.dir/UnitTestVariantArrayHandle.cxx.o.d -o vtkm/cont/testing/CMakeFiles/UnitTests_vtkm_cont_testing.dir/UnitTestVariantArrayHandle.cxx.o -c ../vtkm/cont/testing/UnitTestVariantArrayHandle.cxx
c++: internal compiler error: Killed (program cc1plus)
Please submit a full bug report,
with preprocessed source if appropriate.
See <file:///usr/share/doc/gcc-7/README.Bugs> for instructions.

Running under top reveals that the problem is the compiler is running out of memory. Low priority, of course, but it might be sensible to break this into multiple units as time permits.