include only one variant in compiled code

[kziemianek]

After this change only one expression will be present in compiled code, also there will be no if statement anymore.

Previous version was failing in this case:

#[cfg(feature = "production")]
fn print_prod() {
	info!("Prod")
}

#[cfg(not(feature = "production"))]
fn print_dev() {
	info!("Dev")
}

if_production_or!(
	print_prod(),
	print_dev()
);

105 |         print_dev()
    |         ^^^^^^^^^ not found in this scope

[Kailai-Wang]

Looks good!