head -r320458 (e.g.) amd64 -> powerpc (32-bit) cross-buildworld fails for time libc++ static_asserts and overflow/underflow of long long (system clang/clang++ 4 based build)

[Konstantin Belousov]

On Thu, Jun 29, 2017 at 12:47:10PM +0200, Dimitry Andric wrote:
> One nasty problem with this is that it is not possible to figure out at
> compile time what the size of time_t is.  You always need some sort of
> configure-time test, and an external define.

It is arguably possible, with constexpr.