+# Solaris 8's mkdir -p isn't thread-safe. If you mkdir -p a/b and
+# mkdir -p a/c at the same time, both will detect that a is missing,
+# one will create a, then the other will try to create a and die with
+# a "File exists" error. This is a problem when calling mkinstalldirs
+# from a parallel make. We use --version in the probe to restrict
+# ourselves to GNU mkdir, which is thread-safe.