Change first if conditional so upgrade q only asked if opam installed

scripts/install_build_environment.sh

@@ -6,7 +6,6 @@ then
     then
 	echo "Opam 2.x seems to already exist, exiting..."
 	exit 1
-    fi
     else
 	read -p "This script will upgrade opam to the 2.x series, are you okay with that? (y/n)" choice1
 	case "$choice1" in
@@ -14,6 +13,7 @@ else
 	    n|N ) exit ;;
 	esac
     fi
+fi
 
 sudo apt-get install -y make \
      m4 \