cleverleaf: Intel compiler fails compilation without c++11 flag (#8550) (#8598)

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

@@ -44,3 +44,9 @@ class Cleverleaf(CMakePackage):
     depends_on('hdf5+mpi')
     depends_on('boost')
     depends_on('cmake@3.1:', type='build')
+
+    def flag_handler(self, name, flags):
+        if self.spec.satisfies('%intel') and name in ['cppflags', 'cxxflags']:
+            flags.append(self.compiler.cxx11_flag)
+
+        return (None, None, flags)