Make gemmlowp_headers apex-available for com.android.neuralnetworks.

Test: coral-userdebug build
Bug: 148593574
Change-Id: I300cf8ac971db642988e9bd6676cec3a850655b7
diff --git a/Android.bp b/Android.bp
index 3f1dab4..87e74db 100644
--- a/Android.bp
+++ b/Android.bp
@@ -31,6 +31,11 @@
     vendor_available: true,
     host_supported: true,
     export_include_dirs: ["."],
+    apex_available: [
+        "com.android.neuralnetworks",
+        "test_com.android.neuralnetworks",
+        "//apex_available:platform",
+    ],
 }
 
 subdirs = ["eight_bit_int_gemm"]