main.pro: use qmake/compiler.pri -- the compiler.pri in the root does not exist.
main.pro: use qmake/compiler.pri -- the compiler.pri in the root does not exist.

Apparenty, a lot of our builders didn't catch this, apparently because
they don't clean the Git repo on every build.

Lartza/mumble,Lartza/mumble,Lartza/mumble,Lartza/mumble,Lartza/mumble,Lartza/mumble,Lartza/mumble,Lartza/mumble