-DX64_DEFINED resp. -DRPI_DEFINED need a value for cmake, otherwise there is an error:
$ cmake .. -DRTLSDR=ON -DX64_DEFINED --debug-output
Running with debug output on.
CMake Error: Parse error in command line argument: X64_DEFINED
Should be: VAR:type=value
-DX64_DEFINED
resp.-DRPI_DEFINED
need a value for cmake, otherwise there is an error: