new package: GSL - C++ Guideline Support Library (#9091)

Since "GSL" is a highly overloaded acronym, the package name is "cppgsl".

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

@@ -0,0 +1,51 @@
+##############################################################################
+# Copyright (c) 2013-2018, Lawrence Livermore National Security, LLC.
+# Produced at the Lawrence Livermore National Laboratory.
+#
+# This file is part of Spack.
+# Created by Todd Gamblin, tgamblin@llnl.gov, All rights reserved.
+# LLNL-CODE-647188
+#
+# For details, see https://github.com/spack/spack
+# Please also see the NOTICE and LICENSE files for our notice and the LGPL.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License (as
+# published by the Free Software Foundation) version 2.1, February 1999.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the IMPLIED WARRANTY OF
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the terms and
+# conditions of the GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+##############################################################################
+from spack import *
+
+
+class Cppgsl(CMakePackage):
+    """C++ Guideline Support Library"""
+
+    homepage = "https://github.com/Microsoft/GSL"
+    url      = "https://github.com/Microsoft/GSL/archive/v2.0.0.tar.gz"
+    git      = "https://github.com/Microsoft/GSL.git"
+
+    version('develop', branch='master')
+    version('2.0.0', sha256='6cce6fb16b651e62711a4f58e484931013c33979b795d1b1f7646f640cfa9c8e')
+    version('1.0.0', sha256='9694b04cd78e5b1a769868f19fdd9eea2002de3d4c3a81a1b769209364543c36')
+
+    variant('cxxstd',
+            default='14',
+            values=('14', '17'),
+            multi=False,
+            description='Use the specified C++ standard when building.')
+
+    depends_on('cmake@3.1.3:', type='build')
+
+    def cmake_args(self):
+        args = [
+            '-DGSL_CXX_STANDARD={0}'.format(self.spec.variants['cxxstd'].value)
+        ]
+        return args