Enable host builds for libETC1

Fix checkbuilds - I missed this definition here.

Change-Id: I99c395cc86faed37fad0021bec99a567bee51067
diff --git a/opengl/libs/Android.bp b/opengl/libs/Android.bp
index 813fd99..f28d4ff 100644
--- a/opengl/libs/Android.bp
+++ b/opengl/libs/Android.bp
@@ -2,6 +2,7 @@
 cc_library {
     name: "libETC1",
     srcs: ["ETC1/etc1.cpp"],
+    host_supported: true,
 
     target: {
         android: {