Linkerconfig with namespace contribution

APEX can contribute search paths to linker namespaces.

Bug: 216208308
Test: linkerconfig_diff_test
Change-Id: I3f9b85d7a491b9ac841b0e454c707b4d6c150654
diff --git a/linkerconfig/proto/linker_config.proto b/linkerconfig/proto/linker_config.proto
index fec66c8..dccf311 100644
--- a/linkerconfig/proto/linker_config.proto
+++ b/linkerconfig/proto/linker_config.proto
@@ -34,4 +34,16 @@
 
   // Required libs from the module
   repeated string requireLibs = 4;
+
+  message Contribution {
+    // Target namespace where this module contributes the search paths.
+    string namespace = 1;
+    // Search paths (inc. permitted paths) that this module contributes.
+    // Paths should be related to the current module and can use "${LIB}" variable which is
+    // expanded to "lib" or "lib64".
+    // e.g. ${LIB}/subdir
+    repeated string paths = 2;
+  }
+  // APEX can contribute search paths to specified namespaces.
+  repeated Contribution contributions = 5;
 }