Fix braino in ld config of runtime apex.

Had this fix locally, but forgot to upload it.

Test: CtsJdwpTestCases
Change-Id: I9584246be8cc315bd3e273ef1d4495c9abb57746
diff --git a/build/apex/ld.config.txt b/build/apex/ld.config.txt
index b2637a9..d0145e4 100644
--- a/build/apex/ld.config.txt
+++ b/build/apex/ld.config.txt
@@ -64,6 +64,6 @@
 namespace.runtime.visible = true
 namespace.runtime.links = default
 namespace.runtime.link.default.allow_all_shared_libs = true
-namespace.runtime.links = platform
+namespace.runtime.links += platform
 # TODO(b/119867084): Restrict fallback to platform namespace to PALette library.
 namespace.runtime.link.platform.allow_all_shared_libs = true