Add perf package (#3556)

packages/perf.rb

+require 'package'
+
+class Perf < Package
+  description 'Linux profiling with performance counters'
+  homepage 'https://perf.wiki.kernel.org/index.php/Main_Page'
+  version '4.14'
+  source_url 'file:///dev/null'
+  source_sha256 'e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855'
+
+  # Reuse linux sources if they're already installed
+  depends_on 'linux_sources' => :build
+
+  def self.build
+    Dir.chdir("#{CREW_PREFIX}/src/linux/tools/perf") do
+      system "make WERROR=0 prefix=#{CREW_PREFIX}"
+    end
+  end
+
+  def self.install
+    Dir.chdir("#{CREW_PREFIX}/src/linux/tools/perf") do
+      system 'make',
+             'WERROR=0',
+             'missing_tools=xmlto', # Docs are broken, disable
+             "prefix=#{CREW_PREFIX}",
+             "DESTDIR=#{CREW_DEST_DIR}",
+             'install'
+    end
+  end
+end