add new package : haproxy (#14160)

* add new package : haproxy

* add url_for_version() and refine haproxy build code

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

@@ -0,0 +1,29 @@
+# Copyright 2013-2019 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 Haproxy(MakefilePackage):
+    """
+    HAProxy is a single-threaded, event-driven, non-blocking engine
+    combining a very fast I/O layer with a priority-based scheduler.
+    """
+
+    homepage = "https://www.haproxy.org"
+    url      = "https://www.haproxy.org/download/2.1/src/haproxy-2.1.0.tar.gz"
+
+    version('2.1.1', sha256='57e75c1a380fc6f6aa7033f71384370899443c7f4e8a4ba289b5d4350bc76d1a')
+    version('2.1.0', sha256='f268efb360a0e925137b4b8ed431f2f8f3b68327efb2c418b266e535d8e335a0')
+
+    def url_for_version(self, version):
+        url = "https://www.haproxy.org/download/{0}/src/haproxy-{1}.tar.gz"
+        return url.format(version.up_to(2), version)
+
+    def build(self, spec, prefix):
+        make('TARGET=generic', 'PREFIX=' + prefix)
+
+    def install(self, spec, prefix):
+        install_tree('.', prefix)