Add support for PlayStation platforms (#2562)

* Add new `CATCH_CONFIG` option for using `std::getenv`, because PS does not support env vars
* Add PS to platforms that have disabled posix signals.
* Small workaround for PS toolchain bug that prevents it from compiling `std::set` with lambda based comparator.

CMake/CatchConfigOptions.cmake

@@ -40,6 +40,7 @@ set(_OverridableOptions
   "USE_ASYNC"
   "WCHAR"
   "WINDOWS_SEH"
+  "GETENV"
 )
 
 foreach(OptionName ${_OverridableOptions})