Don't rely on gcc detecting from the passed platforms which prefix to
use, but always specify the prefix nixpkgs expects (or doesn't). This
allows us to work around problems where the configure script would add
prefix where nixpkgs doesn't expect one (if `--target` was specified,
but the same as `--host`) or doesn't add one if nixpkgs expects one (if
`--target` and `--host` are the same, but we are actually cross
compiling, but the relevant parts of the platform are not encoded into
the platform config.
See also ca9be0511b.
This causes some minor ugliness during stdenv bootstrap on powerpc64le
using cross-compiled bootstrap tools. MPFR wants to use decimal floats
by default so they have to be manually disabled in the configure flags
when using cross-compiled bootstrap tools.
The lineage of this particular configure flag traces back to 2010 (!)
It was added in commit: 9b1d5353a9
I've built various cross bootstrap tools and they seem to work fine,
so I don't think this is needed anymore.
This is needed to build grub2 for powerpc64le hosts. Running powerpcle code
on powerpc64le is somewhat analogous to running multiarch i686 code on x86_64,
so it's also useful to have in general.
reasoning:
sjlj (short jump long jump) exception handling makes no sense on x86_64, it's forcably slowing programs down as it produces a constant overhead. On x86_64 we have SEH (Structured Exception Handling) and we should use that. On i686, we do not have SEH, and have to use sjlj with dwarf2. Hence it's now conditional on x86_32
This option can be used to set the “jit” language which enable the
libgccjit functionality. Also adds a “libgccjit” attr which is gcc
built with just jit enabled.
Vladimír Čunát