Cross build with cgo error

[limboinf]

没法在Mac OSX上交叉编译到Linux，Windows，原因是go-sqlite3使用了cgo，错误信息：

# Build for win
go clean
CGO_ENABLED=0 GOOS=windows GOARCH=amd64 go build -ldflags "-X main.Version="1.2""
# ydao/vendor/github.com/mattn/go-sqlite3
vendor/github.com/mattn/go-sqlite3/sqlite3_go18.go:18: undefined: SQLiteConn
vendor/github.com/mattn/go-sqlite3/sqlite3_go18.go:26: undefined: SQLiteConn
vendor/github.com/mattn/go-sqlite3/sqlite3_go18.go:27: undefined: namedValue
vendor/github.com/mattn/go-sqlite3/sqlite3_go18.go:29: undefined: namedValue
vendor/github.com/mattn/go-sqlite3/sqlite3_go18.go:35: undefined: SQLiteConn
vendor/github.com/mattn/go-sqlite3/sqlite3_go18.go:36: undefined: namedValue
vendor/github.com/mattn/go-sqlite3/sqlite3_go18.go:44: undefined: SQLiteConn
vendor/github.com/mattn/go-sqlite3/sqlite3_go18.go:49: undefined: SQLiteConn
vendor/github.com/mattn/go-sqlite3/sqlite3_go18.go:54: undefined: SQLiteStmt
vendor/github.com/mattn/go-sqlite3/sqlite3_go18.go:63: undefined: SQLiteStmt
vendor/github.com/mattn/go-sqlite3/sqlite3_go18.go:36: too many errors
make: *** [release] Error 2

相关链接：mattn/go-sqlite3#384