implement Path::getCurrentExecutablePath for Haiku (#8677) #20290

Job	Run time
build_make (ubuntu:25.10)	5m 29s
build_make (alpine:3.23)	4m 46s
build_make (ubuntu:24.04)	4m 29s
build_cmake (alpine:3.23, false, false)	2m 53s
build_cmake (ubuntu:25.10, true, true)	5m 51s
build_cmake (ubuntu:24.04, true, true)	5m 31s
	28m 59s

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