[Go] Inline optimization flags

https://github.com/golang/go/blob/62ccee49d6d9bdb63841a259d835703ff85ab0b7/src/cmd/compile/internal/gc/inl.go#L10

disabling optimisations
$ -gcflags='-l -N'

More aggressive opt
$ -gcflags='-l -l'

// The debug['l'] flag controls the aggressiveness. Note that main() swaps level 0 and 1,
// making 1 the default and -l disable. Additional levels (beyond -l) may be buggy and
// are not supported.
//      0: disabled
//      1: 80-nodes leaf functions, oneliners, panic, lazy typechecking (default)
//      2: (unassigned)
//      3: (unassigned)
//      4: allow non-leaf functions