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
`libstdc++` and a few other libraries are comiled with the options
set in `EXTRA_TARGET_FLAGS`. Normally, this is filled form
`EXTRA_FLAGS` inside of `builder.sh`, from which it inherits its
optimization option. For cross compilers `EXTRA_TARGET_FLAGS` is
set by a dedicated function that does not specify any optimization,
leading to sub-par runtime performance of many C++ programs.
I hate the thing too even though I made it, and rather just get rid of
it. But we can't do that yet. In the meantime, this brings us more
inline with autoconf and will make it slightly easier for me to write a
pkg-config wrapper, which we need.
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.
ARM ABIs now have a float field. This is used as a fallback to lessen
our use of `platform.gcc.float`. I didn't know what the MIPs convention
is so I kept using `platform.gcc.float` in that case.
