Update WASIp2 bindings to 0.2.12, use exit-with-code (#860)

So far wasi-libc has never updated its wasip2 bindings, and I feel it's
about time this is done. This is used to get access to exit-with-code.
Users needing to use the older version of WASIp2 can continue to use
historical versions of wasi-libc/wasi-sdk, much the same as needing to
use an older LLVM version.

Author: alexcrichton

CMakeLists.txt

@@ -153,7 +153,7 @@ else()
   message(FATAL_ERROR "Unknown WASI version: ${WASI}")
 endif()
 
-set(wasip2-version 0.2.0)
+set(wasip2-version 0.2.12)
 set(wasip3-version 0.3.0)
 
 # =============================================================================

expected/wasm32-wasip2/defined-symbols.txt

@@ -576,6 +576,7 @@ erfl
 errno
 exit
 exit_exit
+exit_exit_with_code
 exit_result_void_void_free
 exp
 exp10

expected/wasm32-wasip2/undefined-symbols.txt

@@ -26,6 +26,7 @@ __wasm_import_environment_get_arguments
 __wasm_import_environment_get_environment
 __wasm_import_environment_initial_cwd
 __wasm_import_exit_exit
+__wasm_import_exit_exit_with_code
 __wasm_import_filesystem_descriptor_drop
 __wasm_import_filesystem_directory_entry_stream_drop
 __wasm_import_filesystem_filesystem_error_code

libc-bottom-half/cloudlibc/src/libc/stdlib/_Exit.c

@@ -10,10 +10,7 @@
 noreturn void _Exit(int status) {
 #if defined(__wasip1__)
   __wasi_proc_exit(status);
-#elif defined(__wasip2__)
-  exit_result_void_void_t exit_status = { .is_err = status != 0 };
-  exit_exit(&exit_status);
-#elif defined(__wasip3__)
+#elif defined(__wasip2__) || defined(__wasip3__)
   if (status >= 0 && status <= 255)
     exit_exit_with_code(status);
   exit_result_void_void_t exit_status = { .is_err = status != 0 };

libc-bottom-half/crt/crt1-command.c

@@ -18,7 +18,7 @@ __attribute__((export_name("_start"))) void _start(void)
 // doing. Given the special nature of this symbol this skip the typical
 // `wit-bindgen` rigamarole and the signature of this function is simple enough
 // that this shouldn't be too problematic (in theory).
-__attribute__((export_name("wasi:cli/run@0.2.0#run"))) int _start(void)
+__attribute__((export_name("wasi:cli/run@0.2.12#run"))) int _start(void)
 #elif defined(__wasip3__)
 __attribute__((export_name("wasi:cli/run@0.3.0#run"))) int _start(void)
 #else