Show build config in dumpsys SurfaceFlinger

This adds a line to the "dumpsys SurfaceFlinger" output that shows
build-time configuration values.

Example:
 Build configuration: [sf HAS_CONTEXT_PRIORITY] [libui] \
  [libgui USE_FENCE_SYNC]

Bug 7206633

Change-Id: Ibe1856b459d34a4be6ee83a4ebfd2807e6cc68a0
diff --git a/libs/gui/GuiConfig.cpp b/libs/gui/GuiConfig.cpp
new file mode 100644
index 0000000..0744e4f
--- /dev/null
+++ b/libs/gui/GuiConfig.cpp
@@ -0,0 +1,38 @@
+/*
+ * Copyright (C) 2012 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <gui/GuiConfig.h>
+
+namespace android {
+
+void appendGuiConfigString(String8& configStr)
+{
+    static const char* config =
+            " [libgui"
+#ifdef USE_FENCE_SYNC
+            " USE_FENCE_SYNC"
+#endif
+#ifdef USE_NATIVE_FENCE_SYNC
+            " USE_NATIVE_FENCE_SYNC"
+#endif
+#ifdef ALLOW_DEQUEUE_CURRENT_BUFFER
+            " ALLOW_DEQUEUE_CURRENT_BUFFER"
+#endif
+            "]";
+    configStr.append(config);
+}
+
+}; // namespace android