darkstat: fix on 10.12 and newer

Closes #19168.

Signed-off-by: FX Coudert <fxcoudert@gmail.com>

Formula/darkstat.rb

@@ -18,6 +18,13 @@ class Darkstat < Formula
     depends_on "autoconf" => :build
   end
 
+  # Patch reported to upstream on 2017-10-08
+  # Work around `redefinition of clockid_t` issue on 10.12 SDK or newer
+  patch do
+    url "https://raw.githubusercontent.com/Homebrew/formula-patches/442ce4a5/darkstat/clock_gettime.patch"
+    sha256 "001b81d417a802f16c5bc4577c3b840799511a79ceedec27fc7ff1273df1018b"
+  end
+
   def install
     system "autoreconf", "-iv" if build.head?
     system "./configure", "--disable-debug", "--prefix=#{prefix}"