src/Makefile_obj.in: fix compile error when using bison 3.6.1

Workaround issue: bison 3.6.1 generated unexpected nested-comment
Closes: verilator#2320
Signed-off-by: Huang Rui <vowstar@gmail.com>

src/Makefile_obj.in

@@ -323,6 +323,12 @@ V3ParseBison.h: V3ParseBison.c
 V3ParseBison.c: verilog.y $(BISONPRE)
 	@echo "If you get errors from verilog.y below, try upgrading bison to version 1.875 or newer."
 	$(PERL) $(BISONPRE) --yacc ${YACC} -d -v -o V3ParseBison.c $<
+	# Unfortunately bison 3.6.1 have break changes caused compile error.
+	# Workaround issue https://github.com/verilator/verilator/issues/2320
+	# This workaround is safe for the old version of bison.
+	# TODO: code should removed when bison fixed the problem.
+	@sed -ie 's#/\* "/\*.*\*/"  \*/##g' V3ParseBison.c
+	@sed -ie 's#/\* "/\*.*\*/"  \*/##g' V3ParseBison.h
 
 V3Lexer_pregen.yy.cpp:	verilog.l V3ParseBison.h $(HEADERS)
 	${LEX} --version