Query for -dip1000

[Per Nordlöw]

Is there a way to query if the -dip1000 flag has been passed to 
the compiler? I need it for enabling certain DIP-1000 escape 
analysis tests only when -dip1000 has been passed.

For instance

     static assert(!__traits(compiles, {
                 char[] f()
                 {
                     char[2] x;
                     return x[].splitterASCII!(_ => _ == ' 
').front;
                 }
             }));

at

https://github.com/nordlow/phobos-next/blob/bd2fe42978aab2313977042c858d77c5766538e8/src/splitter_ex.d#L110

Or do I have to write a trait myself?