Replace LIB_PATH macro with kLibPath

The string is still "lib" or "lib64" with native bridge. It doesn't need
to be configured in the Android.bp file anymore, so move it to a header
file. This change will ensure that ${LIB} expands to the same thing in
both ld.config.txt and DT_RUN_PATH.

Bug: http://b/145197367
Test: manual
Change-Id: Iab87f3156f2984dd3a20e4ccda423892c8b58763
Merged-In: Iab87f3156f2984dd3a20e4ccda423892c8b58763
diff --git a/linker/linker_config.h b/linker/linker_config.h
index 75d9378..6733148 100644
--- a/linker/linker_config.h
+++ b/linker/linker_config.h
@@ -40,6 +40,12 @@
 
 #include <android-base/macros.h>
 
+#if defined(__LP64__)
+static constexpr const char* kLibPath = "lib64";
+#else
+static constexpr const char* kLibPath = "lib";
+#endif
+
 class NamespaceLinkConfig {
  public:
   NamespaceLinkConfig() = default;