Try to fix error on solaris

Add vm_core.h before builtin.h to pack.c for VM_CORE_H_EC_DEFINED. https://rubyci.org/logs/rubyci.s3.amazonaws.com/solaris11s-sunc/ruby-master/log/20191112T102505Z.fail.html.gz ``` compiling dmyenc.c linking miniruby Undefined first referenced symbol in file rb_vm_lvar_exposed pack.o ld: fatal: symbol referencing errors gmake: *** [miniruby] Error 2 ``` 

1 files changed, 1 insertions, 0 deletions

diff --git a/pack.c b/pack.c
index c91531f58d..a4e0882869 100644
--- a/pack.c
+++ b/pack.c
@@ -15,6 +15,7 @@
 #include <ctype.h>
 #include <errno.h>
 #include <float.h>
+#include "vm_core.h"
 #include "builtin.h"

 /*