Avoid duplicate "warning:" or "error:" output #9857

Job	Run time
check-ubuntu-20_04-cmake-gcc	20m 47s
check-ubuntu-20_04-cmake-gcc-KNOWNBUG	2m 38s
check-ubuntu-20_04-make-clang	22m 51s
check-ubuntu-20_04-make-clang-smt-z3	3m 48s
check-ubuntu-20_04-make-gcc	17m 2s
check-ubuntu-22_04-cmake-gcc	19m 45s
check-ubuntu-22_04-cmake-gcc-13	18m 28s
check-ubuntu-22_04-cmake-gcc-32bit	20m 43s
check-ubuntu-22_04-make-clang	17m 50s
check-docker-image	21m 57s
check-macos-11-make-clang	40m 53s
check-macos-12-cmake-clang	35m 39s
check-string-table	2m 40s
check-ubuntu-20_04-cmake-gcc-THOROUGH	8m 15s
check-vs-2019-cmake-build-and-test	52m 25s
check-vs-2022-make-build-and-test	1h 9m 24s
codecov-coverage-report	41m 3s
include-what-you-use	25m 59s
windows-msi-package	3m 49s
	7h 25m 56s

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