Disable dw2-dir-file-name.exp on remote and/or Windows host.

Disable dw2-dir-file-name.exp on remote and/or Windows host.

This test has many hardwired assumptions that pathnames on build and
host are the same, and that POSIX pathname syntax is used.  This
results in dozens of failures on a remote Windows host.  Fixing these
assumptions would involve nontrivial rewrites; meanwhile, let's make
the test results reflect the reality that this testcase isn't supported
on remote host.

2019-08-15  Sandra Loosemore  <sandra@codesourcery.com>

	gdb/testsuite/
	* gdb.dwarf2/dw2-dir-file-name.exp: Skip on remote or
	Windows host.