tests: avoid false-positive failures on linux/sparc64

* tests/init.cfg (require_strace_): Detect a version of strace
that fails on linux/sparc64 for 64-bit executables.  Report and
most of the suggested fix from Bruno Haible:
http://thread.gmane.org/gmane.comp.gnu.coreutils.general/1726/focus=1728

tests/init.cfg

@@ -128,6 +128,15 @@ require_strace_()
 
   strace -qe "$1" echo > /dev/null 2>&1 ||
     skip_ 'strace -qe "'"$1"'" does not work'
+
+  # On some linux/sparc64 systems, strace works fine on 32-bit executables,
+  # but prints only one line of output for every 64-bit executable.
+  strace -o log-help ls --help >/dev/null || framework_failure_
+  n_lines_help=$(wc -l < log-help)
+  rm -f log-help
+  if test $n_lines_help = 0 || test $n_lines_help = 1; then
+    skip_ 'strace produces no more than one line of output'
+  fi
 }
 
 require_setfacl_()