Add new package: findbugs (#17825)

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

+# 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 Findbugs(Package):
+    """a program which uses static analysis to look for bugs in Java code.
+    It is free software, distributed under the terms of the Lesser GNU
+    Public License."""
+
+    homepage = "https://findbugs.sourceforge.net/"
+    url      = "https://sourceforge.net/projects/findbugs/files/findbugs/3.0.1/findbugs-3.0.1.tar.gz"
+    list_url = "https://sourceforge.net/projects/findbugs/files/findbugs"
+    list_depth = 1
+
+    version('3.0.1', sha256='e80e0da0c213a27504ef3188ef25f107651700ffc66433eac6a7454bbe336419')
+    version('3.0.0', sha256='31c75797ead68dbb334fd57bf16f4b7b99c9e266447171453e06fdf673335f33')
+    version('2.0.3', sha256='59ba2a64d786ae5b3fa46e9f9c7bb3ea91c24d43d383c8ef594217f6f51e499f')
+
+    depends_on('java', type=('run'))
+
+    def install(self, spec, prefix):
+        install_tree('.', prefix)