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.

src/catch2/internal/catch_platform.hpp

@@ -28,6 +28,10 @@
 #  if defined( WINAPI_FAMILY ) && ( WINAPI_FAMILY == WINAPI_FAMILY_APP )
 #      define CATCH_PLATFORM_WINDOWS_UWP
 #  endif
+
+#elif defined(__ORBIS__) || defined(__PROSPERO__)
+#  define CATCH_PLATFORM_PLAYSTATION
+
 #endif
 
 #endif // CATCH_PLATFORM_HPP_INCLUDED