Move weak attribute to front (#310)

This is a follow-up based on @sbc100's comments in #306.

Author: abrown

libc-bottom-half/sources/__wasilibc_initialize_environ.c

@@ -11,7 +11,7 @@
 /// Statically-initialize it to an invalid pointer value so that we can
 /// detect if it's been explicitly initialized (we can't use `NULL` because
 /// `clearenv` sets it to NULL.
-char **__wasilibc_environ weak = (char **)-1;
+weak char **__wasilibc_environ = (char **)-1;
 
 // See the comments in libc-environ.h.
 void __wasilibc_ensure_environ(void) {
@@ -87,8 +87,7 @@ void __wasilibc_deinitialize_environ(void) {
 }
 
 // See the comments in libc-environ.h.
-weak
-void __wasilibc_maybe_reinitialize_environ_eagerly(void) {
+weak void __wasilibc_maybe_reinitialize_environ_eagerly(void) {
     // This version does nothing. It may be overridden by a version which does
     // something if `environ` is used.
 }