Is `__GNUC__` defined in dmd when using importC?

[felixfxu]

my dmd is downloaded from the website (not locally compiled from 
source):

>apt search dmd
Sorting... Done
Full Text Search... Done
dmd/now 2.111.0-0 amd64 [installed,local]
   Digital Mars D Compiler

and

> dmd --version
DMD64 D Compiler v2.111.0