Workaround LLVM bug 11663

[xen0n]

Based on this FreeBSD commit, with modification to accomodate the way MIPS ABI is presented on Linux.

[glaubitz]

@alexcrichton I am seeing these stack overflows on Linux/sparc64 again:

running: /usr/bin/cargo build --manifest-path /home/glaubitz/rust/rustc-1.23.0+dfsg1/src/bootstrap/Cargo.toml --verbose --
error: failed to run `rustc` to learn about target-specific information

Caused by:
  process didn't exit successfully: `/usr/bin/rustc - --crate-name ___ --print=file-names -C link-args=-Wl,-z,relro -Zrema0+dfsg1 -Zremap-path-prefix-to=/usr/src/rustc-1.23.0 --target sparc64-unknown-linux-gnu --crate-type bin --crate-type proccess abort signal)
--- stderr

thread 'rustc' has overflowed its stack
fatal runtime error: stack overflow

Looking at lib/builtins/int_lib.h, this particular workaround is missing again.

So, I guess we need to reimport #27, #28, #31, #33 and #34 as LLVM upstream still hasn't fixed this bug (https://bugs.llvm.org/show_bug.cgi?id=11663).

[glaubitz]

I created #35 for convenience. With the #35 merged, the problem goes away again.