Fix sdk-mac build.

Do not use version_script for darwin

Bug: http://b/122886514
Test: make
Change-Id: I8a860e67b0768cce387de1257147e8989f711f06
diff --git a/libnativebridge/Android.bp b/libnativebridge/Android.bp
index a5f0142..c54570e 100644
--- a/libnativebridge/Android.bp
+++ b/libnativebridge/Android.bp
@@ -17,7 +17,15 @@
         "liblog",
     ],
 
-    version_script: "libnativebridge.map.txt",
+    target: {
+        android: {
+            version_script: "libnativebridge.map.txt",
+        },
+        linux: {
+            version_script: "libnativebridge.map.txt",
+        },
+    },
+
     stubs: {
         symbol_file: "libnativebridge.map.txt",
         versions: ["1"],