add new package: yarn (#15562)

var/spack/repos/builtin/packages/yarn/package.py

@@ -0,0 +1,22 @@
+# Copyright 2013-2020 Lawrence Livermore National Security, LLC and other
+# Spack Project Developers. See the top-level COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+from spack import *
+
+
+class Yarn(Package):
+    """Fast, reliable, and secure dependency management."""
+
+    homepage = "https://yarnpkg.com"
+    url      = "https://github.com/yarnpkg/yarn/releases/download/v1.22.4/yarn-v1.22.4.tar.gz"
+
+    version('1.22.4', sha256='bc5316aa110b2f564a71a3d6e235be55b98714660870c5b6b2d2d3f12587fb58')
+    version('1.22.2', sha256='de4cff575ae7151f8189bf1d747f026695d768d0563e2860df407ab79c70693d')
+    version('1.22.1', sha256='3af905904932078faa8f485d97c928416b30a86dd09dcd76e746a55c7f533b72')
+    version('1.22.0', sha256='de8871c4e2822cba80d58c2e72366fb78567ec56e873493c9ca0cca76c60f9a5')
+    version('1.21.1', sha256='d1d9f4a0f16f5ed484e814afeb98f39b82d4728c6c8beaafb5abc99c02db6674')
+
+    def install(self, spec, prefix):
+        install_tree('.', prefix)