Refactor buildvm symbol generation.

Fixes Windows and OSX builds with LUAJIT_DISABLE_JIT.

src/buildvm.h

@@ -34,9 +34,6 @@
 #define LABEL_PREFIX_LIBCF	LABEL_PREFIX "lib_cf_"
 #define LABEL_PREFIX_LIBINIT	LABEL_PREFIX "lib_init_"
 
-/* Extra labels. */
-#define LABEL_ASM_BEGIN		LABEL_PREFIX "vm_asm_begin"
-
 /* Forward declaration. */
 struct dasm_State;
 
@@ -66,6 +63,11 @@ typedef struct BuildReloc {
   int type;
 } BuildReloc;
 
+typedef struct BuildSym {
+  const char *name;
+  int32_t ofs;
+} BuildSym;
+
 /* Build context structure. */
 typedef struct BuildCtx {
   /* DynASM state pointer. Should be first member. */
@@ -78,12 +80,13 @@ typedef struct BuildCtx {
   /* Code and symbols generated by DynASM. */
   uint8_t *code;
   size_t codesz;
-  int npc, nglob, nsym, nreloc;
+  int npc, nglob, nsym, nreloc, nrelocsym;
   void **glob;
-  int *perm;
-  int32_t *sym_ofs;
+  BuildSym *sym;
+  const char **relocsym;
+  int32_t *bc_ofs;
+  const char *beginsym;
   /* Strings generated by DynASM. */
-  const char *const *extnames;
   const char *const *globnames;
   const char *dasm_ident;
   const char *dasm_arch;