Correct run order between tidy and regenerate's deps. Make snowball not fail on Windows (just emit an error).

gradle/generation/regenerate.gradle

@@ -35,7 +35,7 @@ configure([
       Set<Task> deps = regenerate.getTaskDependencies().getDependencies(regenerate)
       def tidy = deps.find { it.name == "tidy" }
       if (tidy) {
-          tidy.dependsOn (deps - [tidy])
+          tidy.mustRunAfter (deps - [tidy])
       }
     }
 }

gradle/generation/snowball.gradle

@@ -90,22 +90,25 @@ configure(project(":lucene:analysis:common")) {
     description "Regenerates snowball stemmers."
     group "generation"
 
+    // Don't even bother adding dependencies.
+    if (Os.isFamily(Os.FAMILY_WINDOWS)) {
+      doFirst {
+        // Just emit a big fat error message but don't fail the build.
+        logger.error("Snowball generation does not work on Windows, use a platform where bash is available.")
+      }
+    } else {
       dependsOn downloadSnowballStemmers
       dependsOn downloadSnowballWebsite
       dependsOn downloadSnowballData
 
       doFirst {
-      if (Os.isFamily(Os.FAMILY_WINDOWS)) {
-        logger.warn("Snowball generation does not work on Windows, use a platform where bash is available.")
-        return
-      }
-
         project.exec {
           executable "bash"
           args = [snowballScript, snowballStemmerDir, snowballWebsiteDir, snowballDataDir, projectDir]
         }
       }
     }
+  }
 
   regenerate.dependsOn snowball, "tidy"
 }