Add ninja

packages/ninja.rb

+require 'package'
+
+class Ninja < Package
+  description 'a small build system with a focus on speed'
+  homepage 'https://ninja-build.org'
+  version '1.7.2'
+  source_url 'https://github.com/ninja-build/ninja/archive/v1.7.2.tar.gz'
+  source_sha256 '2edda0a5421ace3cf428309211270772dd35a91af60c96f93f90df6bc41b16d9'
+
+  depends_on 'python3'
+  depends_on 'unzip'
+
+  def self.build
+    system "python3 configure.py --bootstrap"
+  end
+
+  def self.install
+    system "mkdir -p #{CREW_DEST_DIR}/usr/local/bin"
+    system "cp ninja #{CREW_DEST_DIR}/usr/local/bin/"
+  end
+end