[libstdc++] Add --disable-hosted-libstdcxx, clean up conditionals

[Gabriel Dos Reis]

"Zack Weinberg" <zack@codesourcery.com> writes:

| Gabriel Dos Reis <gdr@integrable-solutions.net> writes:
| 
| > | Technical limitations of Bourne shell unfortunately have to trump
| > | aesthetics.
| >
| > Sure.  But, my motivation was not aesthetics.
| 
| I'm having trouble thinking of a motivation that trumps "we can't do
| that, it doesn't work."

Probably because you stripped too much of the message you're replying to.

-- Gaby