[CMake] Spaces in var=value list in *_command

[Andrew Brownsword]

I’m using the externalproject_add command to build a non-cmake project.  To the build I am passing CXXFLAGS=value, but I cannot manage to get any spaces into the value no matter how I quote, use variables, use escapes, etc.  Searching turns up other people with the same problem and no particularly good solutions.  One example was to use cmake_command -E echo to create a wrapper script that contains the desired string, however this isn’t working for me either (its seems to behave as if the cmake_command variable is empty or undefined).  This seems WAY harder than it should be...