Cristian Adam authored Jul 11, 2018 and Brad King committed Jul 11, 2018

In commit v3.12.0-rc1~20^2 (Move GNU COMPILER_PREDEFINES_COMMAND from
Platform to Compiler, 2018-06-01), `Compiler/GNU.cmake` introduced the
`-dM` flag, which requires `-Wp` prefix for the QNX compiler wrapper.