Fix bug in how Debian packages are built

bash/release.sh

 # This bash file is intended to be used for building .deb release files to be
 # used by pull and push. To use this file just create your own bash file in
 # which you define the APPNAME and DESCRIPTION vars and the
 # copy_release_files() function which copies all the files needed in the
 # distribution in ${ROOT}. Then source this file after those definitions. The
 # resulting .deb will be uploaded to Google Storage with the correct metadata.
 #
 # Follow Debian conventions for file locations. For example:
 #
 # HTML Template files in    /usr/local/share/${APPNAME}/
@@ skipping 58 matching lines @@
         Package: skia-${APPNAME}
         Version: 1.0
         Depends: ${DEPENDS}
         Architecture: amd64
         Maintainer: ${USERNAME}@${HOST}
         Priority: optional
         Description: ${DESCRIPTION}
 EOF
 
 cat <<-EOF > ${ROOT}/DEBIAN/postinst
-#!/bin/sh
+#!/bin/bash
 INIT_SCRIPT="${INIT_SCRIPT}"
 set -e
 if [ -e /bin/systemctl ]
 then
   /bin/systemctl daemon-reload
   /bin/systemctl enable ${SYSTEMD}
   /bin/systemctl restart ${SYSTEMD}
-elif [ -z \$INIT_SCRIPT ]
+elif [ ! -z "\$INIT_SCRIPT" ]
 then
   update-rc.d \$INIT_SCRIPT enable
   service $INIT_SCRIPT start
 fi
 EOF
 chmod 755 ${ROOT}/DEBIAN/postinst
 
 copy_release_files
 
 if [ ! -v BYPASS_GENERATION ]
@@ skipping 25 matching lines @@
     -h x-goog-meta-hash:${HASH} \
     -h x-goog-meta-datetime:${DATETIME} \
     -h x-goog-meta-dirty:${DIRTY} \
     -h "x-goog-meta-note:$1" \
     -h "x-goog-meta-services:${SYSTEMD}" \
     cp ${OUT}/${APPNAME}.deb \
     gs://skia-push/debs/${APPNAME}/${APPNAME}:${USERID}:${DATETIME}:${HASH}.deb
 else
   echo "Upload bypassed."
 fi