yuzu/CMakeLists: Disable unsafe overloads of QProcess' start() function

Other overloads of start() are considerably much safer to use if we ever
need this in the future and need to pass arguments to the program, given
it contains separate parameters for the program path and the arguments
themselves, whereas this unsafe overload contains both as a single
string.

Given the alternatives are much safer, we can disable this.

src/citra_qt/CMakeLists.txt

@@ -231,6 +231,9 @@ target_compile_definitions(citra-qt PRIVATE
 
     # Disable implicit type narrowing in signal/slot connect() calls.
     -DQT_NO_NARROWING_CONVERSIONS_IN_CONNECT
+
+    # Disable unsafe overloads of QProcess' start() function.
+    -DQT_NO_PROCESS_COMBINED_ARGUMENT_START
 )
 
 if (CITRA_ENABLE_COMPATIBILITY_REPORTING)