Cope with missing /usr/sbin/prelink.
* lib/prelink-support.exp (prelink_no):
<result == 1 && $output is "no such file or directory">: New.
(prelink_yes): Likewise. Return on failed prelink_no.
* gdb.base/attach-pie-misread.exp: Load prelink-support.exp. Replace
build_executable by build_executable_own_libs. Replace "prelink -R"
execution by a call of prelink_yes. Comment why "prelink -r" needs no
change.
* gdb.base/break-interp.exp: Load prelink-support.exp. Rename calls of
copy to file_copy. Move setting opts --dynamic-linker and -rpath,
mkdir $dir and ldd its parsing and copying to lib/prelink-support.exp.
Replace build_executable by build_executable_own_libs's function
build_executable_own_libs.
(prelinkNO): Create new stub to call prelink_no.
(prelinkYES): Create new stub to call prelink_yes.
(test_attach): Rename calls of copy to file_copy.
(section_get, prelinkNO_run, prelinkNO, prelinkYES, symlink_resolve)
(copy): Move to ...
* lib/prelink-support.exp: ... a new file. Rename prelinkNO to
prelink_no, prelinkYES to prelink_yes, copy to file_copy.
* gdb.base/prelink.exp: Disable testcase also for is_remote and
skip_shlib_tests. Load prelink-support.exp. Replace gdb_compile with
special flags by gdb_compile_shlib. Replace second gdb_compile by
build_executable_own_libs. Replace "prelink -R" execution by a call of
prelink_yes. Replace "prelink -u" and second "prelink -R" execution by
a second call of prelink_yes. Replace restart commands by
clean_restart.
(prelink): Rename to ...
(seen displacement message): ... this test. Extend its expectation
strictness.
