Generation and comparison of ABI dumps are done on multiple cores
thanks to xargs -P0.
It can accelerate this long step by 5 in my tests.

xargs reports a global error if one of the process has an error.

Running a shell function with xargs requires to export it.
POSIX shell does not support function export except using an "eval trick".
Required variables are also exported.

Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Tested-by: Ferruh Yigit <ferruh.yigit@amd.com>
Reviewed-by: David Marchand <david.marchand@redhat.com>