I am now building a custom debian package from our kernel sources, the 
kernel compile goes fine.  The deb-pkg is failing because the number of 
files passed to xarg is too long.

Error message is.

2018-04-19 07:11:17 - INFO     - | Using default distribution of 'unstable' 
in the changelog
2018-04-19 07:11:17 - INFO     - | Install lsb-release or set 
$KDEB_CHANGELOG_DIST explicitly
2018-04-19 07:11:17 - INFO     - | /usr/bin/xargs: md5sum: Argument list 
too long
2018-04-19 07:11:17 - INFO     - | scripts/package/Makefile:90: recipe for 
target 'deb-pkg' failed
2018-04-19 07:11:17 - INFO     - | make[1]: *** [deb-pkg] Error 126
2018-04-19 07:11:17 - INFO     - | Makefile:1347: recipe for target 
'deb-pkg' failed
2018-04-19 07:11:17 - INFO     - | make: *** [deb-pkg] Error 2
2018-04-19 07:11:17 - INFO     - | WARNING: exit code 2 from a shell 
command.

looks like on large kernel builds the file lists will need to be broken up.