Adjust Makefile for LLVM trunk (16) as of 2022-10-25

llvm/llvm-project@1e4e243
enabled sign-ext and mutable-globals by default, which adds
corresponding __wasm_-prefixed #defines.

Makefile

@@ -632,6 +632,8 @@ check-symbols: startup_files libc
 	@# TODO: Filter out __NO_MATH_ERRNO_ and a few __*WIDTH__ that are new to clang 14.
 	@# TODO: clang defined __FLT_EVAL_METHOD__ until clang 15, so we force-undefine it
 	@# for older versions.
+	@# TODO: Undefine __wasm_mutable_globals__ and __wasm_sign_ext__, that are new to
+	@# clang 16 for -mcpu=generic.
 	$(CC) $(CFLAGS) "$(SYSROOT_SHARE)/include-all.c" \
 	    -isystem $(SYSROOT_INC) \
 	    -std=gnu17 \
@@ -645,6 +647,8 @@ check-symbols: startup_files libc
 	    -U__clang_version__ \
 	    -U__clang_literal_encoding__ \
 	    -U__clang_wide_literal_encoding__ \
+	    -U__wasm_mutable_globals__ \
+	    -U__wasm_sign_ext__ \
 	    -U__GNUC__ \
 	    -U__GNUC_MINOR__ \
 	    -U__GNUC_PATCHLEVEL__ \

expected/wasm32-wasi/posix/predefined-macros.txt

@@ -3099,8 +3099,6 @@
 #define __wasm__ 1
 #define __wasm_atomics__ 1
 #define __wasm_bulk_memory__ 1
-#define __wasm_mutable_globals__ 1
-#define __wasm_sign_ext__ 1
 #define _tolower(a) ((a)|0x20)
 #define _toupper(a) ((a)&0x5f)
 #define acos(x) __tg_real_complex(acos, (x))