Add a little hack to help lcov genhtml find flex and bison source files

Makefile.am

@@ -53,7 +53,9 @@ endif
 code-coverage-html:
 if CODE_COVERAGE_ENABLED
 	@echo "Generating code coverage HTML report (this might take a while)"
+	@cp src/knot/conf/cf-lex.l src/knot/conf/cf-parse.y src/
 	LANG=C $(GENHTML) $(code_coverage_quiet) --prefix $(top_builddir) --output-directory "$(PACKAGE_NAME)-$(PACKAGE_VERSION)-coverage" --title "$(PACKAGE_NAME)-$(PACKAGE_VERSION) Code Coverage" --legend --show-details "$(PACKAGE_NAME)-$(PACKAGE_VERSION)-coverage.info" --ignore-errors source
+	-@rm src/cf-lex.l src/cf-parse.y
 else
 	@echo "You need to run configure with --enable-code-coverage to enable code coverage"
 endif