logstalgia: use new dsl

Formula/logstalgia.rb

@@ -15,7 +15,7 @@ class Logstalgia < Formula
   depends_on 'pcre'
   depends_on :x11
 
-  if ARGV.build_head?
+  if build.head?
     depends_on :automake
     depends_on :libtool
   end
@@ -25,7 +25,7 @@ class Logstalgia < Formula
     ENV.append "CXXFLAGS", "-I#{HOMEBREW_PREFIX}/include"
 
     # Handle building head.
-    system "autoreconf -f -i" if ARGV.build_head?
+    system "autoreconf -f -i" if build.head?
 
     system "./configure", "--disable-dependency-tracking",
                           "--prefix=#{prefix}"