Configure shouldn't send so much stuff to /dev/null

[khwilliamson]

Description

#22728 and #22793 both appear to stem from a hard-to-spot typo in a C program that Configure tries to compile and run. It turns out that that typo causes the compilation to be aborted on some platforms/compilers, but not others. But in all cases, stderr is redirected to
/dev/null, making this hard to diagnose and solve.

We need some mechanism for such failures to be reportable. I believe that there are cases where the compilation will fail, and that is viewed as an indication that the current platform doesn't support the feature the test program is checking on.

A solution that occurs to me is to capture all such things in a temporary file, which normally gets thrown away, but provide a means to dump its contents on demand.