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/atkmm/template

@@ -2,7 +2,7 @@
 pkgname=atkmm
 version=2.22.5
 distfiles="${GNOME_SITE}/atkmm/2.22/$pkgname-$version.tar.bz2"
-build_style=gnu_configure
+build_style=gnu-configure
 configure_args="--disable-documentation"
 short_desc="Set of interfaces for accessibility (C++ bindings)"
 maintainer="Juan RP <xtraeme@gmail.com>"