pg_upgrade: fix -j race condition on Windows Pg_Upgrade cannot write the command string to the log file and then call system() to write to the same file without causing occasional file-share errors on Windows.  So instead, write the command string to the log file after system(), in those cases. Backpatch to 9.3.
pg_upgrade: fix -j race condition on Windows
Pg_Upgrade cannot write the command string to the log file and then call
system() to write to the same file without causing occasional file-share
errors on Windows.  So instead, write the command string to the log file
after system(), in those cases.
Backpatch to 9.3.

pavanvd/postgres-xl,greenplum-db/gpdb,50wu/gpdb,oberstet/postgres-xl,yazun/postgres-xl,zeroae/postgres-xl,jmcatamney/gpdb,lisakowen/gpdb,zeroae/postgres-xl,oberstet/postgres-xl,xinzweb/gpdb,50wu/gpdb,jmcatamney/gpdb,lisakowen/gpdb,yazun/postgres-xl,Postgres-XL/Postgres-XL,techdragon/Postgres-XL,adam8157/gpdb,lisakowen/gpdb,zeroae/postgres-xl,oberstet/postgres-xl,ovr/postgres-xl,adam8157/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,xinzweb/gpdb,yazun/postgres-xl,pavanvd/postgres-xl,jmcatamney/gpdb,greenplum-db/gpdb,lisakowen/gpdb,xinzweb/gpdb,pavanvd/postgres-xl,oberstet/postgres-xl,ashwinstar/gpdb,xinzweb/gpdb,lisakowen/gpdb,ovr/postgres-xl,Postgres-XL/Postgres-XL,techdragon/Postgres-XL,xinzweb/gpdb,lisakowen/gpdb,adam8157/gpdb,adam8157/gpdb,techdragon/Postgres-XL,ovr/postgres-xl,techdragon/Postgres-XL,yazun/postgres-xl,yazun/postgres-xl,xinzweb/gpdb,ashwinstar/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,ashwinstar/gpdb,ashwinstar/gpdb,jmcatamney/gpdb,techdragon/Postgres-XL,adam8157/gpdb,greenplum-db/gpdb,ashwinstar/gpdb,lisakowen/gpdb,zeroae/postgres-xl,xinzweb/gpdb,jmcatamney/gpdb,50wu/gpdb,adam8157/gpdb,50wu/gpdb,Postgres-XL/Postgres-XL,pavanvd/postgres-xl,ashwinstar/gpdb,greenplum-db/gpdb,pavanvd/postgres-xl,50wu/gpdb,ovr/postgres-xl,greenplum-db/gpdb,ashwinstar/gpdb,50wu/gpdb,jmcatamney/gpdb,zeroae/postgres-xl,oberstet/postgres-xl,adam8157/gpdb,adam8157/gpdb,Postgres-XL/Postgres-XL,ovr/postgres-xl,lisakowen/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,xinzweb/gpdb,Postgres-XL/Postgres-XL,50wu/gpdb,50wu/gpdb