Segfault when trying to build with mismatching architecture and pointer width

[trajing]

Trying to build for arm-none-eabi as though it had a pointer width of 64 bits causes an "error: could not compile core" with no further elaboration, and rebuilding with --verbose reveals that rustc segfaults.

To reproduce:

xargo new --lib segfault-repro
cd segfault-repro
echo '{"llvm-target": "arm-none-eabi", "data-layout": "e-m:e-p:64:32-i64:64-v128:64:128-a:0:32-n32-S64", "linker-flavor": "gcc", "target-endian": "little", "target-pointer-width": "64", "target-c-int-width": "32", "arch": "arm", "os": "none"}' > arm-segfault.json
xargo build --target arm-segfault --verbose

Changing the llvm target to "aarch64-none-elf" and the arch to "aarch64", or changing the target file to claim that pointers are 32-bit, will fix the segfault.

I'm actually not sure if this is a rustc bug or a xargo bug, as I lack the knowledge to do this with rustc without xargo -- sorry if this is in the wrong place!