cmake: sync warnings with autotools v2 By some reason gcc reports next error: ../http.c:3330:11: warning: assignment discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers] value = ""; Only under -Wwrite-strings, well this is logical, but this information does not reflected in any documentation. Follow-up: 8348b413 ("cmake: add various warning flags like autotools has") f