Skip bz2 GH-20807 test when less than 13 GiB of memory is available

The decompressed output of this test peaks at more than 12 GiB of RSS.
On smaller machines, such as the 7 GB GitHub-hosted runners used for
private repositories, this exhausts the whole VM and the OOM killer takes
the test runner down with it, so the job dies with a runner shutdown
signal instead of a test failure.

Gate the test on MemAvailable from /proc/meminfo like the other
resource-heavy tests gate on memory, so it keeps running on the 16 GB
public runners and skips itself elsewhere.

Author: bukka

ext/bz2/tests/gh20807.phpt

@@ -12,6 +12,12 @@ if (PHP_OS === 'FreeBSD') die('skip Worker does not handle OOM gracefully');
 if (PHP_OS_FAMILY === 'Darwin') die('skip Too slow');
 if (PHP_INT_SIZE !== 8) die('skip Only for 64-bit systems');
 if (getenv('SKIP_ASAN')) die('skip ASAN makes this test too slow');
+// The decompressed output needs more than 12 GiB of memory at its peak, which
+// takes down smaller machines (e.g. 7 GB CI runners) with the OOM killer.
+$memInfo = @file_get_contents('/proc/meminfo');
+if ($memInfo && preg_match('/MemAvailable:\s+(\d+) kB/', $memInfo, $m) && $m[1] < 13 * 1024 * 1024) {
+    die('skip Insufficient available memory (less than 13 GiB)');
+}
 ?>
 --FILE--
 <?php