testsuite: drop the symlink-escape oracle when it runs but crashes (Solaris)

The da7c4208 oracle-exec guard only caught OSError (can't-exec / ENOEXEC, on the
BSDs and macOS).  Solaris execs the Linux x86-64 old_versions/rsync_3.2.7 binary
without ENOEXEC but it SIGSEGVs, so subprocess.run('--version') returned -11
without raising and ORACLE_BIN stayed set -- the oracle daemon launch then died
("rsyncd exited before listening on port 12910, status=-11") and failed the test.

Require the probe to exit cleanly (returncode == 0); a non-zero/signal exit, a
hang (TimeoutExpired), or a can't-exec (OSError) all degrade to the static
contract.

testsuite/daemon-symlink-escape-matrix_test.py

@@ -78,14 +78,19 @@ if RSYNC_PEER != RSYNC:
 elif (_repo / 'old_versions' / 'rsync_3.2.7').is_file():
     ORACLE_BIN = str(_repo / 'old_versions' / 'rsync_3.2.7')
 
-# The in-tree oracle is a Linux x86-64 static binary, so on a non-Linux runner
-# (BSD/macOS/Solaris) it is present but cannot exec.  Probe it and degrade to the
-# static contract on any exec failure rather than crashing with ENOEXEC.
+# The in-tree oracle is a Linux x86-64 static binary, so on a non-Linux runner it
+# is present but not usable: a BSD/macOS host refuses to exec it (ENOEXEC), while
+# Solaris execs it but it crashes (SIGSEGV).  Probe it with `--version` and degrade
+# to the static contract unless it ran cleanly (rc == 0) -- catching can't-exec
+# (OSError), a hang (TimeoutExpired), and a non-zero/signal exit alike -- rather
+# than later crashing the oracle daemon launch.
 if ORACLE_BIN:
     try:
-        subprocess.run([ORACLE_BIN, '--version'],
-                       stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL, timeout=15)
-    except OSError:
+        _probe = subprocess.run([ORACLE_BIN, '--version'],
+                                stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL, timeout=15)
+        if _probe.returncode != 0:
+            ORACLE_BIN = None
+    except (OSError, subprocess.TimeoutExpired):
         ORACLE_BIN = None
 
 TYPES = ('rel-within', 'rel-outside', 'rel-transits', 'abs-outside', 'abs-inside')