fix decl of ruby_single_main_ractor

On windows, MJIT doesn't work without this patch because of
the declaration of ruby_single_main_ractor. This patch fix this
issue and move the definition of it from ractor.c to vm.c to locate
near place of ruby_current_vm_ptr.

1 files changed, 1 insertions, 1 deletions

diff --git a/vm_sync.h b/vm_sync.h
index 8244b6173e..14b63f3017 100644
--- a/vm_sync.h
+++ b/vm_sync.h
@@ -31,7 +31,7 @@ void rb_vm_barrier(void);
 #include "vm_core.h"
 #endif
 
-extern struct rb_ractor_struct *ruby_single_main_ractor; // ractor.c
+RUBY_EXTERN struct rb_ractor_struct *ruby_single_main_ractor; // ractor.c
 
 static inline bool
 rb_multi_ractor_p(void)