Allow to get <vendor-ndk><version> from matrix

Test: vts_treble_vintf_vendor_test
Test: libvintf_test
Bug: 78117402
Change-Id: I4da7d23a354a59aaa27d0b61f8fd98a54f0fb1ec
diff --git a/CompatibilityMatrix.cpp b/CompatibilityMatrix.cpp
index 338e5be..97f8977 100644
--- a/CompatibilityMatrix.cpp
+++ b/CompatibilityMatrix.cpp
@@ -439,5 +439,9 @@
     return found;
 }
 
+std::string CompatibilityMatrix::getVendorNdkVersion() const {
+    return type() == SchemaType::DEVICE ? device.mVendorNdk.version() : "";
+}
+
 } // namespace vintf
 } // namespace android