compile_pkgs: move set -e from hashbang

Setting -e in hashbang is not a good idea as users might just run it by
some other interpreter and that way removing (without noticing it) that
option.

compile_pkgs

-#!/bin/bash -e
+#!/bin/bash
 # OpenWRT compilation script
 # (C) 2018-2020 CZ.NIC, z.s.p.o.
 #
@@ -14,6 +14,7 @@
 #
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
+set -e
 shopt -s nullglob
 
 # Step list that is run when no commands are specified