add package builder and make packagePath in BuildDir relative to options.GOPATH/src
add package builder and make packagePath in BuildDir relative to options.GOPATH/src

ebroder/gopherjs,jeremyschlatter/gopherjs,ebroder/gopherjs,gopherjs/gopherjs,Archs/gopherjs,bpowers/gopherjs,Yanjing123/gopherjs,albrow/gopherjs,albrow/gopherjs,Archs/gopherjs,rasata/gopherjs,jargv/gopherjs,jeremyschlatter/gopherjs,gopherjs/gopherjs,flimzy/gopherjs,flimzy/gopherjs,nmfzone/gopherjs,govlas/gopherjs,rasata/gopherjs,nmfzone/gopherjs,Yanjing123/gopherjs,gopherjs/gopherjs,govlas/gopherjs,jeremyschlatter/gopherjs,albrow/gopherjs,roth1002/gopherjs,gopherjs/gopherjs,Yanjing123/gopherjs,roth1002/gopherjs,flimzy/gopherjs,Archs/gopherjs,rasata/gopherjs,gopherjs/gopherjs,bpowers/gopherjs,ebroder/gopherjs,roth1002/gopherjs,bpowers/gopherjs,jargv/gopherjs,govlas/gopherjs,nmfzone/gopherjs,jargv/gopherjs