[flang] Added preprocessor directives to limit the use of non-inline...

[flang] Added preprocessor directives to limit the use of non-inline ExpressionBase<A>::derived to GCC on Mac (inlined on all other platforms)

Original-commit: flang-compiler/f18@b38b31909a4d30e3cfd77353d44ecff06ef425da
Reviewed-on: https://github.com/flang-compiler/f18/pull/248