AssembleVintf: PRODUCT_ => PLATFORM_ for system sdk versions

Test: libvintf_test
Bug: 69088799
Change-Id: Iafe51d06972760cd01df78acb79bcac421b53c8e
diff --git a/AssembleVintf.cpp b/AssembleVintf.cpp
index f7f1fb4..d17f1c5 100644
--- a/AssembleVintf.cpp
+++ b/AssembleVintf.cpp
@@ -306,7 +306,7 @@
                 halManifest->framework.mVendorNdks.emplace_back(std::move(v));
             }
 
-            for (auto&& v : getEnvList("PRODUCT_SYSTEMSDK_VERSIONS")) {
+            for (auto&& v : getEnvList("PLATFORM_SYSTEMSDK_VERSIONS")) {
                 halManifest->framework.mSystemSdk.mVersions.emplace(std::move(v));
             }
         }