Update build_style for all templates.

- There's no need to set build_style for custom-install (default).
- gnu_{configure,makefile} renamed to gnu-{configure,makefile}.

srcpkgs/gnome-shell-extensions/template

@@ -3,7 +3,6 @@ pkgname=gnome-shell-extensions
 version=3.2.0
 homepage="http://live.gnome.org/GnomeShell/Extensions"
 distfiles="${GNOME_SITE}/$pkgname/3.2/$pkgname-$version.tar.xz"
-build_style=custom-install
 short_desc="GNOME Shell extensions"
 maintainer="Juan RP <xtraeme@gmail.com>"
 license="GPL-2"