Avoid sync failures if libgav1 isn't present

PiperOrigin-RevId: 273734495

extensions/av1/build.gradle

@@ -54,13 +54,15 @@ android {
     }
     }
 }
 }
 
 
-// Check that the Android NDK and CMake are present, to avoid gradle sync
-// failures if they aren't installed. To use the extension it is necessary to
-// install the NDK and CMake from the SDK Manager.
+// Check that the Android NDK, CMake and libgav1 are present, to avoid gradle
+// sync failures if the tools aren't installed or libgav1 is missing. To use
+// the extension it is necessary to install the NDK and CMake from the SDK
+// Manager and fetch libgav1 following the steps in README.
 def ndkDirectory = project.android.ndkDirectory
 def ndkDirectory = project.android.ndkDirectory
 def sdkDirectory = project.android.sdkDirectory
 def sdkDirectory = project.android.sdkDirectory
 if (ndkDirectory != null && !ndkDirectory.toString().isEmpty()
 if (ndkDirectory != null && !ndkDirectory.toString().isEmpty()
-        && new File(sdkDirectory.toString() + '/cmake').exists()) {
+        && new File(sdkDirectory.toString() + '/cmake').exists()
+        && project.file('src/main/jni/libgav1').exists()) {
     android.externalNativeBuild.cmake.path = 'src/main/jni/CMakeLists.txt'
     android.externalNativeBuild.cmake.path = 'src/main/jni/CMakeLists.txt'
     android.externalNativeBuild.cmake.version = '3.7.1+'
     android.externalNativeBuild.cmake.version = '3.7.1+'
 }
 }