Define __LONG_MAX in alltypes.h (#20930)

This is followup to #20752 which was supposed to define __LONG_MAX
rather than LONG_MAX.

You can see the effect of this change on some struct layouts in musl
that contain checks like `#if __LONG_MAX > 0x7fffffff`.  Since
`__LONG_MAX` (and internal-only macro) is now correctly defined we
get some slightly different values/layouts in libc.

Author: sbc100

src/generated_struct_info32.json

@@ -293,13 +293,13 @@
         "F_DUPFD": 0,
         "F_GETFD": 1,
         "F_GETFL": 3,
-        "F_GETLK": 5,
+        "F_GETLK": 12,
         "F_GETOWN": 9,
         "F_GETOWN_EX": 16,
         "F_SETFD": 2,
         "F_SETFL": 4,
-        "F_SETLK": 6,
-        "F_SETLKW": 7,
+        "F_SETLK": 13,
+        "F_SETLKW": 14,
         "F_SETOWN": 8,
         "F_UNLCK": 2,
         "File::DataFileKind": 1,

src/generated_struct_info64.json

@@ -1421,7 +1421,7 @@
             "iov_len": 8
         },
         "msghdr": {
-            "__size__": 48,
+            "__size__": 56,
             "msg_iov": 16,
             "msg_iovlen": 24,
             "msg_name": 0,

system/lib/compiler-rt/lib/sanitizer_common/sanitizer_platform_limits_posix.h

@@ -445,8 +445,7 @@ struct __sanitizer_file_handle {
 };
 #endif
 
-// These fields are not actually pointers, and so wasm64 must use unsigned and not uptr for them
-#if SANITIZER_APPLE || SANITIZER_EMSCRIPTEN
+#if SANITIZER_APPLE
 struct __sanitizer_msghdr {
   void *msg_name;
   unsigned msg_namelen;

system/lib/libc/musl/arch/emscripten/bits/alltypes.h

@@ -4,7 +4,7 @@
 
 #define __BYTE_ORDER __LITTLE_ENDIAN
 
-#define LONG_MAX  __LONG_MAX__
+#define __LONG_MAX  __LONG_MAX__
 
 #define _Addr __PTRDIFF_TYPE__
 #define _Int64 __INT64_TYPE__