fix /tmp has no writable permission if it is symbolic link (#19591)

fix #19438
diff --git a/src/main/java/com/google/devtools/build/lib/sandbox/LinuxSandboxedSpawnRunner.java b/src/main/java/com/google/devtools/build/lib/sandbox/LinuxSandboxedSpawnRunner.java
index 3b2582f..29d342e 100644
--- a/src/main/java/com/google/devtools/build/lib/sandbox/LinuxSandboxedSpawnRunner.java
+++ b/src/main/java/com/google/devtools/build/lib/sandbox/LinuxSandboxedSpawnRunner.java
@@ -427,7 +427,7 @@
     }
     FileSystem fs = sandboxExecRoot.getFileSystem();
     writableDirs.add(fs.getPath("/dev/shm").resolveSymbolicLinks());
-    writableDirs.add(fs.getPath("/tmp"));
+    writableDirs.add(fs.getPath("/tmp").resolveSymbolicLinks());
 
     return writableDirs.build();
   }