Enable ASTC on supported builds only

To temporarily work around build issues related to Google3 integration,
make ASTC support optional and only enable it for CMake, Chromium, and
Android builds.

Bug: b/150600814
Change-Id: Iac6a404322c65a6f2727807ea8af2edfb219a5a2
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/41828
Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Sean Risser <srisser@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
diff --git a/src/Android.bp b/src/Android.bp
index a400a4c..2f8683a 100644
--- a/src/Android.bp
+++ b/src/Android.bp
@@ -617,6 +617,7 @@
     cflags: [
         "-DLOG_TAG=\"swiftshader\"",
         "-DSWIFTSHADER_EXTERNAL_MEMORY_ANDROID_HARDWARE_BUFFER",
+        "-DSWIFTSHADER_ENABLE_ASTC",  // TODO(b/150130101)
     ],
 
     srcs: [