AC_LIBTOOL_PROG_CC_C_O assumes cwd needn't be writable

[Jens Petersen]

I received the following bug report:

        http://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=89887

which describes how icc apparently hits the following problem described
in the source of the above macro:

   # According to Tom Tromey, Ian Lance Taylor reported there are C compilers
   # that will create temporary files in the current directory regardless of
   # the output directory.  Thus, making CWD read-only will cause this test
   # to fail, enabling locking or at least warning the user not to do parallel
   # builds.
   chmod -w .

Comments?

Jens