test-path-utils: fix normalize_path_copy output buffer size

test-path-utils: fix normalize_path_copy output buffer size

The normalize_path_copy function needs an output buffer that
is at least as long as its input (it may shrink the path,
but never expand it). However, this test program feeds it
static PATH_MAX-sized buffers, which have no relation to the
input size.

In the normalize_ceiling_entry case, we do at least check
the size against PATH_MAX and die(), but that case is even
more convoluted. We normalize into a fixed-size buffer, free
the original, and then replace it with a strdup'd copy of
the result. But normalize_path_copy explicitly allows
normalizing in-place, so we can simply do that.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>