Make users of WorkRequestHandler do System.exit at the end, to prevent hanging threads from keeping the worker alive.

RELNOTES: none
PiperOrigin-RevId: 435284030

src/java_tools/buildjar/java/com/google/devtools/build/buildjar/BazelJavaBuilder.java

diff --git a/src/java_tools/buildjar/java/com/google/devtools/build/buildjar/BazelJavaBuilder.java b/src/java_tools/buildjar/java/com/google/devtools/build/buildjar/BazelJavaBuilder.java
index 6939bfc..aebee7b 100644
--- a/src/java_tools/buildjar/java/com/google/devtools/build/buildjar/BazelJavaBuilder.java
+++ b/src/java_tools/buildjar/java/com/google/devtools/build/buildjar/BazelJavaBuilder.java
@@ -55,6 +55,8 @@
         workerHandler.processRequests();
       } catch (IOException e) {
         System.err.println(e.getMessage());
+      } finally {
+        // Prevent hanging threads from keeping the worker alive.
         System.exit(1);
       }
     } else {