GRBL has certainly become popular in recent years.
I haven't yet tested this post processor on a GRBL, but if anyone would like to test and make suggestions for improvements, I would be very grateful.
The main change to this post from the default post processor is the replacement of drilling canned cycles with G0/G1 moves.
The 'Drill' post processor property is:
{$g0} {$_x} {$_y}
{$g0} Z{$mop.retractheight}
{$g1} {$_z} {$_f}
{$g0} Z{$mop.clearanceplane}
and 'Drill Dwell' is:
{$g0} {$_x} {$_y}
{$g0} Z{$mop.retractheight}
{$g1} {$_z} {$_f}
G4 {$p}
{$g0} Z{$mop.clearanceplane}
Peck drilling is currently not supported as this would require the post processor definitions to be able to handle more complex loops or scripts.
A post build command could be created to handle this.
I hope this post is useful starting point.