Silence compiler warning about using variable uninitialized.
Silence compiler warning about using variable uninitialized.

With GCC 8, -O1, I was getting this:

In file included from ../../../src/include/postgres.h:47,
                 from resgroupcmds.c:14:
resgroupcmds.c: In function ‘AlterResourceGroup’:
../../../src/include/c.h:852:4: error: ‘cpuset’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
    strncpy(_dst, (src), _len); \
    ^~~~~~~
resgroupcmds.c:374:14: note: ‘cpuset’ was declared here
  const char *cpuset;
              ^~~~~~

It's a false warning, all the code paths that lead here initialize
'cpuset', but apparently GCC doesn't see that with -O1.

ashwinstar/gpdb,greenplum-db/gpdb,xinzweb/gpdb,greenplum-db/gpdb,ashwinstar/gpdb,50wu/gpdb,ashwinstar/gpdb,jmcatamney/gpdb,adam8157/gpdb,greenplum-db/gpdb,50wu/gpdb,xinzweb/gpdb,greenplum-db/gpdb,xinzweb/gpdb,lisakowen/gpdb,adam8157/gpdb,xinzweb/gpdb,lisakowen/gpdb,50wu/gpdb,adam8157/gpdb,greenplum-db/gpdb,50wu/gpdb,50wu/gpdb,lisakowen/gpdb,adam8157/gpdb,ashwinstar/gpdb,jmcatamney/gpdb,xinzweb/gpdb,adam8157/gpdb,greenplum-db/gpdb,xinzweb/gpdb,xinzweb/gpdb,greenplum-db/gpdb,jmcatamney/gpdb,lisakowen/gpdb,50wu/gpdb,adam8157/gpdb,ashwinstar/gpdb,jmcatamney/gpdb,50wu/gpdb,50wu/gpdb,greenplum-db/gpdb,ashwinstar/gpdb,ashwinstar/gpdb,jmcatamney/gpdb,lisakowen/gpdb,adam8157/gpdb,lisakowen/gpdb,ashwinstar/gpdb,jmcatamney/gpdb,jmcatamney/gpdb,lisakowen/gpdb,adam8157/gpdb,xinzweb/gpdb,jmcatamney/gpdb,lisakowen/gpdb