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/adobe-flash-plugin/template

@@ -16,7 +16,6 @@ fi
 distfiles="${_eula} ${_disttarball}"
 checksum="${_eulacksum} ${_distcksum}"
 noextract=yes
-build_style=custom-install
 short_desc="Adobe Flash Player plugin"
 maintainer="Juan RP <xtraeme@gmail.com>"
 long_desc="