sandbox: Allow UNIX sockets on macOS even when block-network is used.

Closes #3444.

PiperOrigin-RevId: 163047183
diff --git a/src/main/java/com/google/devtools/build/lib/sandbox/DarwinSandboxedSpawnRunner.java b/src/main/java/com/google/devtools/build/lib/sandbox/DarwinSandboxedSpawnRunner.java
index 90e9b2c..1c9f098 100644
--- a/src/main/java/com/google/devtools/build/lib/sandbox/DarwinSandboxedSpawnRunner.java
+++ b/src/main/java/com/google/devtools/build/lib/sandbox/DarwinSandboxedSpawnRunner.java
@@ -248,6 +248,7 @@
         out.println("(deny network*)");
         out.println("(allow network* (local ip \"localhost:*\"))");
         out.println("(allow network* (remote ip \"localhost:*\"))");
+        out.println("(allow network* (remote unix-socket))");
       }
 
       // By default, everything is read-only.