Ensure realpath and gawk are installed

realpath is required for patching linux and gawk is required for the build
```
==== patching  Linux ====
/home/debian/work/onie/build-config/scripts/cp-machine-patches: line 30: realpath: command not found
/home/debian/work/onie/build-config/scripts/cp-machine-patches: line 31: realpath: command not found
/home/debian/work/onie/build-config/scripts/cp-machine-patches: line 32: realpath: command not found
/home/debian/work/onie/build-config/scripts/cp-machine-patches: line 70: : No such file or directory
make: *** [/home/debian/work/onie/build/fsl_p2020rdbpca-r0/stamp/kernel-patch] Error 1

make: *** Waiting for unfinished jobs....
```