Move the declaration of `rb_path_check` #627

Job	Run time
make (check, cppflags=-DVM_CHECK_MODE)	8m 13s
make (check, i686)	11m 8s
make (check, --disable-yjit)	6m 49s
make (check, --enable-shared --enable-load-relative)	7m 24s
make (test-bundler-parallel, 50)	26m 58s
make (test-bundled-gems)	16m 1s
make (check, ubuntu-20.04)	9m 23s
make (check, ubuntu-24.04)	8m 36s
Ubuntu result	1s
	1h 34m 33s

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