Update to the latest wasi-libc (#283)

Update to wasi-libc a1c7c2c7a4b2813c6f67bd2ef6e0f430d31cebad
 - Don't use sbrk(0) to determine the initial heap size (WebAssembly/wasi-libc#377)
 - Fix more headers to avoid depending on `max_align_t` (WebAssembly/wasi-libc#375)
 - Use `ENOENT` rather than `ENOTCAPABLE` for missing preopens. (WebAssembly/wasi-libc#370)
 - Adjust Makefile for LLVM trunk (16) as of 2022-11-08 (WebAssembly/wasi-libc#344)