Add new package: slf4j (#18042)

var/spack/repos/builtin/packages/slf4j/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 Slf4j(Package):
+    """The Simple Logging Facade for Java (SLF4J) serves as a simple facade
+    or abstraction for various logging frameworks (e.g. java.util.logging,
+    logback,log4j) allowing the end user to plug in the desired logging
+    framework at deployment time."""
+
+    homepage = "http://www.slf4j.org/"
+    url      = "https://github.com/qos-ch/slf4j/archive/v_1.7.30.tar.gz"
+
+    version('1.7.30',       sha256='217519588d0dd1f85cee2357ca31afdd7c0a1a8a6963953b3bf455cf5174633e')
+    version('1.7.29',       sha256='e584f1f380d8c64ed8a45944cec3c2fb4d6b850783fd5bc166a9246bc8b6ac56')
+    version('1.7.28',       sha256='14063bfcbc942bda03e07759e64307163c1646d70a42c632f066812a8630eec7')
+    version('1.7.27',       sha256='238883cab9808a5cd58cf5245f9f13ac645c9fca878b60d959e00fc4ac588231')
+    version('1.7.26',       sha256='dc422820f92e581241c4cfe796d01531d12bad3dc04225bdb315761871156942')
+
+    depends_on('maven', type='build')
+    depends_on('java@8', type=('build', 'run'))
+
+    def install(self, spec, prefix):
+        mvn = which('mvn')
+        mvn('package', '-DskipTests')
+        install_tree('.', prefix)