Add a lock file around building the loom cache. Regenerate if the lock file exists.

This helps to ensure that failed or canceled builds do not cause the cache to be left in an undetectable invalid state.

src/main/java/net/fabricmc/loom/extension/LoomGradleExtensionImpl.java

@@ -69,6 +69,7 @@ public class LoomGradleExtensionImpl extends LoomGradleExtensionApiImpl implemen
 	private NamedMinecraftProvider<?> namedMinecraftProvider;
 	private IntermediaryMinecraftProvider<?> intermediaryMinecraftProvider;
 	private InstallerData installerData;
+	private boolean refreshDeps;
 
 	public LoomGradleExtensionImpl(Project project, LoomFiles files) {
 		super(project, files);
@@ -83,7 +84,15 @@ public class LoomGradleExtensionImpl extends LoomGradleExtensionApiImpl implemen
 			provider.getIntermediaryUrl()
 					.convention(getIntermediaryUrl())
 					.finalizeValueOnRead();
+
+			provider.getRefreshDeps().set(project.provider(() -> LoomGradleExtension.get(project).refreshDeps()));
 		});
+
+		refreshDeps = project.getGradle().getStartParameter().isRefreshDependencies() || Boolean.getBoolean("loom.refresh");
+
+		if (refreshDeps) {
+			project.getLogger().lifecycle("Refresh dependencies is in use, loom will be significantly slower.");
+		}
 	}
 
 	@Override
@@ -227,12 +236,19 @@ public class LoomGradleExtensionImpl extends LoomGradleExtensionApiImpl implemen
 			builder.forceDownload();
 		}
 
-		// TODO
-		//builder.executor();
-
 		return builder;
 	}
 
+	@Override
+	public boolean refreshDeps() {
+		return refreshDeps;
+	}
+
+	@Override
+	public void setRefreshDeps(boolean refreshDeps) {
+		this.refreshDeps = refreshDeps;
+	}
+
 	@Override
 	protected <T extends IntermediateMappingsProvider> void configureIntermediateMappingsProviderInternal(T provider) {
 		provider.getMinecraftVersion().set(getProject().provider(() -> getMinecraftProvider().minecraftVersion()));