#1967 SNMP build fails on debian

[dr_mohan]

The build system fails due to a random path generation when running net_snmp_config --cflags.
The output currently contains
-O2 -fdebug-prefix-map=/build/net-snmp-OeyA43/net-snmp-5.7.3+dfsg=.

It is not processed well by the acinclude.m4 due to a missing space in the perl command line.
SNMPFLAGS=${net_snmp_config:-net-snmp-config} --cflags | perl -p -e 's/-O\S*//g'

Thanks to Adrian Bunk for supplying the attached patch. This could be checked in as soon as we submit an update to the debian release.

[dr_mohan]

More details on this could be found at
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=870733

[dr_mohan]

Fixed with checkin #7719