build-infra: We must be able to force static linking of stdc++

In configure, if we can't compile with a static stdc++ (.a), we silently fall back to dynamic linking (.so). (Or not quite silently, a single non conspicous line of output is emitted about this.)

We never want to do that on official builds. We must have a way of ensuring that we build with static linking, or do not build at all.

I propose that we change the configure flag --disable-static-link-stdc++ into:
--with-stdc++lib=<static>,<dynamic>,<default>
where:
* default would be the following mode of first trying static and then falling back to dynamic,
* static would be: force static, or fail, and
* dynamic would be: force dynamic, or fail.

Otherwise this might cause a lot of trouble when compiling 32-bit libs on 64-bit Linux.