Drop -O2

otherwise uuu aborts with an invalid pointer at the very end

https://github.com/NXPmicro/mfgtools/issues/75

I'd rather not debug this further until we forwarded to a newer version (#2 (closed))

This avoids

$ uuu flash_devkit.lst 
uuu (Universal Update Utility) for nxp imx chips -- libuuu_1.2.31-11-g5df7059

Enjoy auto [tab] command complete by put below script into /etc/bash_completion.d/uuu
  _uuu_autocomplete()
  {
       COMPREPLY=($(/usr/bin/uuu $1 $2 $3))
  }
  complete -o nospace -F _uuu_autocomplete  uuu

Success 1    Failure 0                                                                                                                                                                                            
                                                                                                                                                                                                                   
1:1    4/ 4   [Done                        ] FB: Done                                                                                                                                                              
munmap_chunk(): invalid pointer
Aborted (core dumped)

Would be cool to merge this quickly so @david.boddie can make the docs point to the deb.