Don't make class SementicContext::Empty final.
Don't make class SementicContext::Empty final.

The class does not implement the pure virtual methods so can
not be considered 'final'. Clang 10 and 11 complain about this.

Context: https://github.com/chipsalliance/Surelog/issues/3081
Signed-off-by: Henner Zeller <259ad50fabbfd39355f36ecd6c0afca541ea66ef@acm.org>

antlr/antlr4,antlr/antlr4,parrt/antlr4,parrt/antlr4,parrt/antlr4,antlr/antlr4,ericvergnaud/antlr4,parrt/antlr4,ericvergnaud/antlr4,ericvergnaud/antlr4,antlr/antlr4,antlr/antlr4,parrt/antlr4,parrt/antlr4,ericvergnaud/antlr4,antlr/antlr4,ericvergnaud/antlr4,antlr/antlr4,antlr/antlr4,parrt/antlr4,antlr/antlr4,ericvergnaud/antlr4,ericvergnaud/antlr4,parrt/antlr4,parrt/antlr4,ericvergnaud/antlr4,ericvergnaud/antlr4,parrt/antlr4,antlr/antlr4,ericvergnaud/antlr4