compute-PATCHVERSION: Do not produce output when awk fails
compute-PATCHVERSION uses awk to produce a shell script that is
subsequently executed to update shell variables which are then printed
as the patchversion.
Some versions of awk, most notably bysybox-gawk do not understand the
awk program and fail to run. This results in no script generated as
output, and printing the initial values of the shell variables as
the patchversion.
When the awk program fails to run produce 'exit 1' as the shell script
to run instead. That prevents printing the stale values, generates no
output, and generates invalid rpm spec file down the line. Then the
problem is flagged early and should be easier to diagnose.