Wierd segfault in compiler when certain tests are included in check-fast

[brson]

If I uncomment the xfail-fast line in either linked-failure or lots-a-fail the compiler will fail to build librun_pass_stage2.so with backtraces like

#0  0x08637d5d in glue_take531 ()
#1  0x086621cf in glue_take2656 ()
#2  0xf7f309ba in map::mk_hashmap::hashmap::method::items () from /home/banderson/Dev/rust/build/stage2/libstd.so
#3  0x08296b72 in middle::resolve::resolve_imports ()
#4  0x08292475 in middle::resolve::resolve_crate ()
#5  0x086d8917 in driver::rustc::compile_input::thunk7985 ()
#6  0x085cc08a in driver::rustc::time ()
#7  0x085cfa67 in driver::rustc::compile_input ()
#8  0x085f418a in driver::rustc::main ()
#9  0x08607d35 in _rust_main ()
#10 0x086debcc in _rust_main_wrap ()
#11 0xf7fa9b41 in task_start_wrapper (a=0xf6b2c010) at ../src/rt/rust_task.cpp:149
#12 0xdeadbeef in ?? ()
#13 0xf6b2c010 in ?? ()
#14 0x00006c40 in ?? ()
#15 0x00000000 in ?? ()