update build script

scripts/build-images.sh

 #!/bin/bash
 set -ex
 
-export GLUON_RELEASE="0.15.2"
+export GLUON_RELEASE="2020.2.3-4"
 export GLUON_SITEDIR=..
 export FORCE_UNSAFE_CONFIGURE=1
 export GLUON_AUTOUPDATER_ENABLED=1
@@ -14,11 +14,10 @@ fi
 
 THREADS=$((($(nproc)+1) / 2))
 THREADS=$((($(nproc)+1) ))
-THREADS="1"
 
 # FLAGS="-j 1 V=sc"
-FLAGS="-j $THREADS V=s"
-# FLAGS="-j $(nproc)"
+# FLAGS="-j $THREADS"
+FLAGS="-j $(nproc)"
 
 make -C gluon update