CPack does not support -DVAR=VALUE style
Although the "standard" style is
cmake -D VAR=VALUE, cmake does support
cmake -DVAR=VALUE style. It's also documented in https://cmake.org/cmake/help/v3.20/manual/cmake.1.html:
This option may also be given as a single argument:
If you are accustomed to the former one (without separating space) it's unexpected that
cpack do not support this style as well.