Fix the linkerconfig host binary to not depend on libc++.so.

Test: build/soong/scripts/build-aml-prebuilts.sh runtime-module-host-exports
  Check with ldd that the linkerconfig binary in
  out/aml/soong/mainline-sdks/runtime-module-host-exports-current.zip
  isn't missing any DSO's.
Bug: 145934348
Change-Id: I08676a5d9c7ec3e76462fb74e882f81802528b98
diff --git a/Android.bp b/Android.bp
index cc1c847..32f7b93 100644
--- a/Android.bp
+++ b/Android.bp
@@ -119,6 +119,9 @@
             // libraries, so enable this only on device.
             static_executable: true,
         },
+        host: {
+            stl: "c++_static",  // Link libc++ statically.
+        },
     },
 }