IconMan: suppress `-Wformat-overflow=` #2496

Job	Run time
notifications	4s
build (ubuntu-latest, autotools, gcc)	1m 28s
build (ubuntu-latest, autotools, clang)	1m 28s
build (ubuntu-latest, meson, gcc)	1m 10s
build (ubuntu-latest, meson, clang)	1m 7s
build (alpine, autotools, gcc)	1m 14s
build (alpine, autotools, clang)	1m 3s
build (alpine, meson, gcc)	49s
build (alpine, meson, clang)	44s
	9m 7s

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