OK, when I blow out my install directory and start from scratch it is failing on a different error:
[ 35%] Building CXX object Externals/glslang/CMakeFiles/glslang.dir/glslang/OSDependent/Unix/ossource.cpp.o
[ 35%] Linking CXX static library libglslang.a
[ 35%] Built target glslang
Makefile:170: recipe for target 'all' failed
make: *** [all] Error 2
[ 35%] Building CXX object Externals/glslang/CMakeFiles/glslang.dir/glslang/OSDependent/Unix/ossource.cpp.o
[ 35%] Linking CXX static library libglslang.a
[ 35%] Built target glslang
Makefile:170: recipe for target 'all' failed
make: *** [all] Error 2
