cppunit: support cxxstd. (#10888)

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

@@ -13,3 +13,15 @@ class Cppunit(AutotoolsPackage):
     url = "http://dev-www.libreoffice.org/src/cppunit-1.13.2.tar.gz"
 
     version('1.13.2', '0eaf8bb1dcf4d16b12bec30d0732370390d35e6f')
+
+    variant('cxxstd',
+            default='default',
+            values=('default', '98', '11', '14', '17'),
+            multi=False,
+            description='Use the specified C++ standard when building.')
+
+    def setup_environment(self, spack_env, run_env):
+        cxxstd = self.spec.variants['cxxstd'].value
+        cxxstdflag = '' if cxxstd == 'default' else \
+                     getattr(self.compiler, 'cxx{0}_flag'.format(cxxstd))
+        spack_env.append_flags('CXXFLAGS', cxxstdflag)