libf2c

[Dave Love]

I'm afraid I don't understand building Fortran these days, but the new
libf2c process doesn't look right to me.  I did a bootstrap, and
libf2c was configured with an installed compiler (an older gcc, as
this is a Linux box), reading my site autoconf config.site and cache.
It was then built with xgcc (as I expected).

Originally the configuration was careful to avoid
potentially-misleading autoconf configuration files (including
clobbering things with `make clean', contra GNU standards) and ensure
it did everything with GCC_FOR_TARGET (or whetever the old make
variable was called).  I can't immediately point to anything mixing
the compilers can break but what work I've done on the runtime has
always assumed the target compiler is used generally.

[Sorry for getting this stuff wrong in the first place.]