main/asciidoctor: upgrade to 1.5.6.1 and modernize abuild

main/asciidoctor/APKBUILD

 # Contributor: Seung Soo Mun <hamletmun@gmail.com>
 # Maintainer: Natanael Copa <ncopa@alpinelinux.org>
-_gemname=asciidoctor
-pkgname=$_gemname
-pkgver=1.5.5
-pkgrel=1
-pkgdesc="A text processor for converting AsciiDoc markup into HTML 5, DocBook 4.5 and other formats."
-url="http://rubygems.org/gems/$_gemname"
+pkgname=asciidoctor
+pkgver=1.5.6.1
+pkgrel=0
+pkgdesc="A text processor for converting AsciiDoc markup into HTML 5, DocBook 4.5 and other formats"
+url="http://rubygems.org/gems/$pkgname"
 arch="noarch"
 license="MIT"
 depends="ruby"
-makedepends=""
-source="http://gems.rubyforge.org/gems/$_gemname-$pkgver.gem"
-
-build() {
-	return 0
-}
+source="http://gems.rubyforge.org/gems/$pkgname-$pkgver.gem"
 
 package() {
-	local _gemdir="$(ruby -rubygems -e'puts Gem.default_dir')"
+	local gemdir="$(ruby -rubygems -e 'puts Gem.default_dir')"
 
-	gem install --local --install-dir "$pkgdir"/$_gemdir \
-		--ignore-dependencies --verbose --no-document \
-		"$srcdir"/$_gemname-$pkgver.gem || return 1
+	gem install \
+		--local \
+		--install-dir "$pkgdir"/$gemdir \
+		--ignore-dependencies \
+		--verbose \
+		--no-document \
+		"$srcdir"/$pkgname-$pkgver.gem
 
-	rm -rf "$pkgdir"/$_gemdir/cache
+	rm -rf "$pkgdir"/$gemdir/cache
 
 	cd "$pkgdir"
-	for i in usr/lib/ruby/gems/*/bin/*; do
+	local i; for i in usr/lib/ruby/gems/*/bin/*; do
 		if [ -e "$i" ]; then
 			mkdir -p "$pkgdir"/usr/bin
 			ln -s /$i "$pkgdir"/usr/bin/
@@ -34,6 +32,4 @@ package() {
 	done
 }
 
-md5sums="c6ef0cdd20c48687d9f9afcb22ca76d0  asciidoctor-1.5.5.gem"
-sha256sums="87effa3de95919df880aab04c6c29c89255ce671abce361da476208734a5424e  asciidoctor-1.5.5.gem"
-sha512sums="31876c94dab7eba96baaa273e02a54afb23b5b666eb504e26518103350c9c872db9c1d88965a6d8023fa02a1eee05a4abe984b545859d8d92897d6d799f70335  asciidoctor-1.5.5.gem"
+sha512sums="cb23ab539b16b064e4a21575420abdaab34e20b7650a43b47df68ded1a424d1ab265c88102d4f3d3422bd30952fd93db7de254d61fdc253d17ffd93f1345bcdf  asciidoctor-1.5.6.1.gem"