new package: librsb (#14455)

* new package: librsb

* flake8, be good

* no hardocded FC=gfortran

var/spack/repos/builtin/packages/librsb/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 Librsb(AutotoolsPackage):
+    """librsb : A shared memory parallel sparse matrix computations
+    library for the Recursive Sparse Blocks format"""
+
+    homepage = "http://librsb.sourceforge.net/"
+    url      = "http://download.sourceforge.net/librsb/librsb-1.2.0.8.tar.gz"
+    list_url = "https://sourceforge.net/projects/librsb/files/"
+
+    version('1.2.0.8',   '8bebd19a1866d80ade13eabfdd0f07ae7e8a485c0b975b5d15f531ac204d80cb')
+
+    depends_on('zlib')
+    conflicts('%clang')
+
+    def configure_args(self):
+        args = [
+            '--enable-openmp',
+            '--with-zlib',
+            '--enable-fortran-module-install',
+            'CPPFLAGS={0}'.format(self.spec['zlib'].headers.include_flags),
+            'CFLAGS=-O3',
+            'LDFLAGS={0}'.format(self.spec['zlib'].libs.search_flags)
+        ]
+        return args