Fix shebang in generated script

Author: TheAssassin

linuxdeploy-plugin-gtk.sh

@@ -177,14 +177,14 @@ HOOKSDIR="$APPDIR/apprun-hooks"
 HOOKFILE="$HOOKSDIR/linuxdeploy-plugin-gtk.sh"
 mkdir -p "$HOOKSDIR"
 cat > "$HOOKFILE" <<\EOF
-#! /bin/bash
+#! /usr/bin/env bash
 
 gsettings get org.gnome.desktop.interface gtk-theme 2> /dev/null | grep -qi "dark" && GTK_THEME_VARIANT="dark" || GTK_THEME_VARIANT="light"
 APPIMAGE_GTK_THEME="${APPIMAGE_GTK_THEME:-"Adwaita:$GTK_THEME_VARIANT"}" # Allow user to override theme (discouraged)
 
 # in case we run from an AppImage, we use the $APPDIR environment variable as a template for the temporary directory that should be created
 # this allows users to attribute the tempdir to the running AppImage
-if [[ "$APPDIR" != "" ]]; then
+if [ "$APPDIR" != "" ]; then
     tempdir_template="$APPDIR".ld-p-gtk-tmp
 else
     tempdir_template=/tmp/.ld-p-gtk-tmp-XXXXXX