Set BLD_ARCH from /etc/os-release only if other methods fail
Set BLD_ARCH from /etc/os-release only if other methods fail

Co-authored-by: Bradford D. Boyle <ff602883ccbb5041987b5dada3a6394497630732@pivotal.io>
Co-authored-by: Jesse Zhang <6775950e159d0bc2e58935ca2201ba88526dddf0@pivotal.io>

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