Make `make test` depend on build/emp
Make `make test` depend on build/emp

Otherwise, tests can fail in a non-obvious way.

markpeek/empire,lihuanghai/empire,iserko/empire,mhahn/empire,mhahn/empire,zhakui/empire,markpeek/empire,remind101/empire,no2key/empire,zofuthan/empire,no2key/empire,mhahn/empire,remind101/empire,remind101/empire,vfulco/empire,zofuthan/empire,iserko/empire,zhakui/empire,iserko/empire,lihuanghai/empire,vfulco/empire