posix: Fix tst-execvpe5 for --enable-hardcoded-path-in-tests

This patch fixes the posix/tst-execvpe5 invocation when GLIBC is
configured with --enable-hardcoded-path-in-tests which fails with:

$ cat  posix/tst-execvpe5.out
Wrong number of arguments (4)

Checked on x86-64 and powerpc64le.

	* posix/tst-execvpe5.c (do_test): Fix fix test invocation when
	configured with --enable-hardcoded-path-in-tests.