rgtk on Windows compiler error

[dubcanada]

While trying to compile rgtk for Windows I keep getting a LLVM assertion failed error.

$ make RUST_BACKTRACE=1
 Building rgtk.rlib
rustc -g --cfg GTK_3_10 -L target/ src/rgtk.rs --out-dir target/
error: internal compiler error: unexpected failure
note: the compiler hit an unexpected failure path. this is a bug.
note: we would appreciate a bug report: http://doc.rust-lang.org/complement-bugr
eport.html
note: run with `RUST_BACKTRACE=1` for a backtrace
task 'rustc' failed at 'assertion failed: index < LLVMCountParams(llfn)', C:\bot
\slave\nightly-win\build\src\librustc_llvm\lib.rs:1950

stack backtrace:
   1: 0x6a181f84
   2: 0x61f88a1c
   3: 0x61f8866d
   4:   0x972548
   5: 0x71044180
   6: 0x70f42679

make: *** [rgtk-build] Error 101

[klutzy]

Fixed by #16484.