It would, in effect, make gcc (and MSVC) into "obscure platforms," or at least non-tier-1.

I remember when Mozilla had trouble when they ran out of virtual memory space in the linker (see https://bugzilla.mozilla.org/show_bug.cgi?id=709193 , but this wasn't the first time that happened) and caused serious churn for the Windows build because Visual Studio was their only option. To be sure, this was exacerbated because VS was and is a proprietary product, but if you're going to bet that clang doesn't suffer some similar critical failure in the future, maybe you shouldn't bet every single tier-1 build of your core product.