[php-src] Issue #21799: phar: phar_stream_close silently discards phar_stream_flush failure

Issue: https://github.com/php/php-src/issues/21799
Author: iliaal

`phar_stream_close` in `ext/phar/stream.c` calls `phar_stream_flush` but discards its return value, always returning 0 (success) from `fclose()` even when the flush failed.

If `phar_stream_flush` encounters a write error (e.g. out of disk space while committing phar modifications), the application gets no indication of failure from `fclose($fp)`.

Location: `phar_stream_close` — `phar_stream_flush(stream);` return value is silently dropped.

Fix: capture the flush return value and return it from `phar_stream_close`.