Makefile: avoid generate parser.go everytime (#2281)
Makefile: avoid generate parser.go everytime (#2281)

introduce a parserlib PHONY, and other rules depend on it, rather than parser.
if parser.go already exists and not older than parser.y, avoid generate it.
XuHuaiyu/tidb,kyle-wang/tidb,zimulala/tidb,simon-xia/tidb,liyu4/tidb,pingcap/tidb,Cofyc/tidb,ngaut/tidb,pingcap/tidb,zimulala/tidb,mccxj/tidb,Cofyc/tidb,tiancaiamao/tidb,andelf/tidb,wusphinx/tidb,yuanwhy/tidb,louishust/tidb,myrice/tidb,CodeRushing/tidb,anywhy/tidb,spongedu/tidb,myrice/tidb,kyle-wang/tidb,simon-xia/tidb,anywhy/tidb,kyle-wang/tidb,kyle-wang/tidb,Nify/tidb,qhsong/tidb,pingcap/tidb,astaxie/tidb,c4pt0r/tidb,cosmtrek/tidb,c4pt0r/tidb,silentred/tidb,JinheLin/tidb,astaxie/tidb,pingcap/tidb,ueizhou/tidb,mccxj/tidb,gaocegege/tidb,wusphinx/tidb,JinheLin/tidb,ngaut/tidb,8cbx/tidb,silenceper/tidb,silenceper/tidb,zs634134578/tidb,louishust/tidb,ming-relax/tidb,tiancaiamao/tidb,yangwenmai/tidb,kyle-wang/tidb,ueizhou/tidb,c4pt0r/tidb,liyu4/tidb,ngaut/tidb,ngaut/tidb,qhsong/tidb,ngaut/tidb,yangwenmai/tidb,ngaut/tidb,andelf/tidb,gaocegege/tidb,CodeRushing/tidb,EvilMcJerkface/tidb,c4pt0r/tidb,pingcap/tidb,silentred/tidb,c4pt0r/tidb,XuHuaiyu/tidb,c4pt0r/tidb,qiuyesuifeng/tidb,coocood/tidb,coocood/tidb,EvilMcJerkface/tidb,zs634134578/tidb,8cbx/tidb,cosmtrek/tidb,pingcap/tidb,ming-relax/tidb,qiuyesuifeng/tidb,spongedu/tidb,kyle-wang/tidb,Nify/tidb,yuanwhy/tidb