Assertion in build on Linux x86

[mzabaluev]

The recent master tree fails the build on Linux (3.8.8-203.fc18.i686 #1 SMP Wed Apr 24 13:33:43 UTC 2013 i686 i686 i386 GNU/Linux) with gcc 4.7.2 20121109 (Red Hat 4.7.2-8).

rustc: /home/mzabaluev/src/rust/src/rt/rust_run_program.cpp:205: RunProgramResult rust_run_program(const char**, void*, const char*, int, int, int): Assertion `!result && "chdir failed"' failed.
/bin/sh: line 1: 20745 Segmentation fault i686-unknown-linux-gnu/stage1/bin/rustc --cfg stage1 -O --target=i686-unknown-linux-gnu -o i686-unknown-linux-gnu/stage1/lib/rustc/i686-unknown-linux-gnu/lib/libcore.so /home/mzabaluev/src/rust/src/libcore/core.rc

The failure bisects to 91aeecf.

[Dretch]

@graydon suggested that the FFI can have issues when returning structs, so I guess that might somehow be causing this issue.

I am currently re-writing more of rust_run_program.cpp in rust (see #2674) ... which I should imagine will fix this issue.

[nikomatsakis]

definitely reproducible.

[brson]

This is a problem only in stage0. The FFI works correctly (in this case) after stage0. Making a snapshot would resolve this, but unfortunately incoming is still broken.

[mzabaluev]

Latest incoming builds without error. Thank you.