Declare a task's outputs, enabling incremental build and caching

This specific task runs an external command, and we consider the task
successful if that command exits without error.  We don't actually
examine the stdout or stderr of the command being run.

However, it is still useful to log the stdout and stderr to a file,
and to declare that file to be the output of the task.  Otherwise, the
task has no declared outputs at all.  A task with no outputs is
ineligible for caching and is always considered to be out-of-date.

squash! Declare a task's outputs, enabling incremental build and caching

com.ibm.wala.cast.test/build.gradle

@@ -111,6 +111,15 @@ model {
 
 			// all combined as a colon-delimited path list
 			args pathElements.join(':')
+
+			// log output to file, although we don't validate it
+			final def outFile = file("$temporaryDir/stdout-and-stderr.log")
+			outputs.file outFile
+			doFirst {
+				final def fileStream = new FileOutputStream(outFile)
+				standardOutput fileStream
+				errorOutput fileStream
+			}
 		}
 
 		check.dependsOn checkSmoke_main