Fix Cranelift extern C ABI on Windows #47

Job	Run time
fmt + clippy	37s
runtime smoke	44s
native tests (x86_64-apple-darwin)	5m 26s
SIMD contract (Cranelift)	41s
parse conformance	42s
type + lowering conformance	44s
backend features (llvm-backend)	1m 47s
native tests (x86_64-unknown-linux-gnu)	2m 28s
backend features (default)	51s
native tests (x86_64-pc-windows-msvc)	5m 26s
	19m 26s

Provide feedback