fixup! Update GCC version #2431

Job	Run time
build_system	24s
duplicates	2s
build (gcc-15.deb, --std-tests)	5m 55s
build (gcc-15.deb, --test-libcore)	14m 37s
build (gcc-15.deb, --extended-rand-tests)	8m 25s
build (gcc-15.deb, --extended-regex-example-tests)	7m 5s
build (gcc-15.deb, --extended-regex-tests)	11m 37s
build (gcc-15.deb, --test-successful-rustc --nb-parts 2 --current-part 0)	11m 14s
build (gcc-15.deb, --test-successful-rustc --nb-parts 2 --current-part 1)	11m 51s
build (gcc-15.deb, --projects)	11m 27s
build (gcc-15-without-int128.deb, --std-tests)	6m 16s
build (gcc-15-without-int128.deb, --test-libcore)	15m 4s
build (gcc-15-without-int128.deb, --extended-rand-tests)	8m 42s
build (gcc-15-without-int128.deb, --extended-regex-example-tests)	6m 49s
build (gcc-15-without-int128.deb, --extended-regex-tests)	11m 47s
build (gcc-15-without-int128.deb, --test-successful-rustc --nb-parts 2 --current-part 0)	11m 31s
build (gcc-15-without-int128.deb, --test-successful-rustc --nb-parts 2 --current-part 1)	11m 29s
build (gcc-15-without-int128.deb, --projects)	11m 15s
	2h 45m 30s

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