desktop/piecannon: capture output of mvn command so we can display it to the user, capture error code so we can pass it upstream

(cherry picked from commit 2f7761bac7)

desktop/piecannon

@@ -8,5 +8,13 @@ STUB_POM="<project xmlns='http://maven.apache.org/POM/4.0.0' xmlns:xsi='http://w
 STUB_POM_FILE=/tmp/pc.xml
 echo $STUB_POM > $STUB_POM_FILE
 
-RESULT=$(mvn -f $STUB_POM_FILE -B exec:java -Dexec.mainClass=$PC_CLASS -Dexec.arguments=$1 -Dorg.slf4j.simpleLogger.defaultLogLevel=WARN | tail -n 1)
+OUTPUT=$(mvn -f $STUB_POM_FILE -B exec:java -Dexec.mainClass=$PC_CLASS -Dexec.arguments=$1 -Dorg.slf4j.simpleLogger.defaultLogLevel=WARN)
+EXEC_RESULT=$?
+echo "$OUTPUT"
+
+if [ $EXEC_RESULT != 0 ]; then
+    exit $EXEC_RESULT;
+fi
+
+RESULT=$(echo "$OUTPUT" | tail -n 1)
 xdg-open $RESULT