Statically link libstdc++ for distribution

[brson]

Binary incompatibilities in libstdc++ are a big source of problems for us. For snapshots we work around this with static linking. Is there any reason we shouldn't do this for our main distributables as well?

cc #17194

cc @alexcrichton

[alexcrichton]

Sadly I've found this to not help whenever I've needed it to in the past. Frequently it's not just libstdc++ that's "too new", but it's also libc that's "too new".

I think that our snapshot builders have an old libc, but I don't actually know if they're linking against it. They may be picking up a libc that was installed with gcc 4.7 (a "too new" libc).

All-in-all, there'd be a few lingering questions for me:

• This prevents dynamically loading any C++ code, is that desirable? This is largely relevant because we currently support dynamically opening syntax extensions. This would prevent anyone from adding optimization passes to LLVM I think, but that may not necessarily be the end of the world.
• Does this actually fix the problem? The libc errors that I've seen after statically linking libstdc++ in the past worry me.

I suspect the answer is "yes, we should statically link libstdc++ for our distribution purposes." We may have to investigate the libc issue further, but this is a step forward!

[alexcrichton]

Closing, this is now done.