libcpp: Make static checkers happy about makeuname2c [PR106778]

libcpp: Make static checkers happy about makeuname2c [PR106778]

The assertion ensures that we point within the image and at a byte
we haven't touched yet (or at least that it isn't the first byte
of an already stored tree), some static checker was unhappy about
first checking that it is zero and only afterwards checking that it
is within bounds.

2022-08-31  Jakub Jelinek  <jakub@redhat.com>

	PR preprocessor/106778
	* makeuname2c.cc (write_nodes): Reverse order of && operands in
	assert.