CI/rtp.io: handle "/" in branch names (i.e feature/xyz) correctly #485

Job	Run time
build_and_test (22.04, gcc-12)	11m 25s
build_and_test (22.04, gcc)	9m 49s
build_and_test (22.04, clang-arm32-qemu-cross)	1h 18m 53s
build_and_test (22.04, clang-15)	8m 8s
build_and_test (22.04, clang-12)	7m 50s
build_and_test (20.04, gcc-9)	9m 18s
build_and_test (20.04, clang)	6m 37s
build_and_test (20.04, gcc)	8m 42s
build_and_test (22.04, clang-arm64-qemu-cross)	1h 20m 4s
build_and_test (22.04, clang)	7m 46s
build_and_test (22.04, clang-11)	7m 55s
build_and_test (20.04, clang-9)	6m 51s
build_and_test (20.04, gcc-10)	8m 11s
build_and_test (22.04, gcc-arm32-qemu-cross)	1h 5m 55s
build_and_test (22.04, gcc-arm64-qemu-cross)	1h 1m 0s
build_and_test (22.04, clang-13)	6m 40s
build_and_test (22.04, clang-14)	7m 53s
build_and_test (22.04, gcc-11)	10m 20s
build_and_test (24.04, clang-18)	6m 52s
build_and_test (24.04, clang-17)	6m 57s
build_and_test (24.04, clang-16)	6m 8s
build_and_test (20.04, clang-10)	7m 0s
build_and_test (24.04, clang-19)	6m 18s
build_and_test (24.04, gcc-13)	8m 44s
build_and_test (24.04, gcc-14)	8m 52s
build_and_test (24.04, clang)	6m 49s
build_and_test (24.04, gcc)	8m 58s
all_done / notify_slack	4s
	7h 49m 59s

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