Fix the symtab2gb dependency on ansi-c

This directory dependency should have been added when the dependency on
the ansi-c library was added to the symtab2gb makefile. This currently
missing dependency results in sporadic build failures.

Author: thomasspriggs

src/Makefile

@@ -91,7 +91,7 @@ memory-analyzer.dir: util.dir goto-programs.dir langapi.dir linking.dir \
 	                   ansi-c.dir
 
 symtab2gb.dir: util.dir goto-programs.dir langapi.dir linking.dir \
-               json.dir json-symtab-language.dir
+               json.dir json-symtab-language.dir ansi-c.dir
 
 # building for a particular directory