Support pseudo macro mnemonics (for RISC-V) in the frontend

src/asm_tables_amd64.cpp

@@ -522,6 +522,14 @@ struct Asm_amd64 {
 		return M_INVALID;
 	}
 
+	enum PseudoMacroMnemonic : u8 {
+		PseudoMacroMnemonic_INVALID,
+		PseudoMacroMnemonic_COUNT
+	};
+
+	PseudoMacroMnemonic pseudo_macro_mnemonic_lookup(String const &name) {
+		return PseudoMacroMnemonic_INVALID;
+	}
 
 	Mnemonic mnemonic_lookup(String const &name) {
 		Mnemonic *found = string_map_get(&mnemonic_map, name);