Bump external/bpf_conformance from `b544539` to `011874f` #156

Job	Run time
build_ubuntu (Debug, tests)	32m 28s
build_windows (Debug, tests)	43m 53s
build_ubuntu (Debug, library)	1m 8s
build_windows (Debug, library)	4m 40s
build_ubuntu (Release, tests)	6m 24s
build_windows (Release, tests)	10m 14s
build_ubuntu (Release, library)	1m 22s
build_windows (Release, library)	5m 19s
	1h 45m 28s

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