Add product_available to product available modules

vendor_available modules were available to product modules.
However, not all vendor_available modules are required to be
available to product modules. Some modules want to be available only
to product modules but not vendor modules.

To cover the requirement, we separate product_available from
vendor_available.
vendor_available will not provide product available module.

Bug: 150902910
Test: build
Change-Id: I3fcce553f52fe98542b7c44711a75fc7d633997f
diff --git a/Android.bp b/Android.bp
index 4d89cf8..be4d6d2 100644
--- a/Android.bp
+++ b/Android.bp
@@ -105,6 +105,7 @@
 cc_library_headers {
     name: "llvm-headers-no-generated-headers",
     vendor_available: true,
+    product_available: true,
     host_supported: true,
     // TODO(b/153609531): remove when no longer needed.
     native_bridge_supported: true,
@@ -128,6 +129,7 @@
 cc_library_headers {
     name: "llvm-headers",
     vendor_available: true,
+    product_available: true,
     host_supported: true,
     // TODO(b/153609531): remove when no longer needed.
     native_bridge_supported: true,
@@ -210,6 +212,7 @@
     host_supported: true,
     name: "libLLVM_android",
     vendor_available: true,
+    product_available: true,
     defaults: [
         "llvm-defaults",
         "force_build_llvm_components",