LLVM assertion in crushtool crate

[pietroalbini]

The crushtool crate fails to compile when LLVM assertions are enabled:

rustc: /checkout/src/llvm/lib/IR/Type.cpp:241: static llvm::IntegerType *llvm::IntegerType::get(llvm::LLVMContext &, unsigned int): Assertion `NumBits >= MIN_INT_BITS && "bitwidth too small"' failed.

This is not a regression, it's confirmed to also fail on 1.28.0 (alt builds are not available past that). You might want to remove the crate's lockfile if you test it locally.

[nikic]

Assertion occurs via SelectionDAGBuilder::lowerRangeToAssertZExt(), likely fixed by llvm-mirror/llvm@3000523.

[nikic]

Verified that this is indeed fixed on master. The last LLVM upgrade pulled in the fix.