Set no_default_deps in shared libc++ builds

TBR=dpranke
BUG=845700

Change-Id: I71f45f6c95c20ac0a779116e0ae8f542e614db6e
diff --git a/third_party/libc++/BUILD.gn b/third_party/libc++/BUILD.gn
index db05234..6cd5a55 100644
--- a/third_party/libc++/BUILD.gn
+++ b/third_party/libc++/BUILD.gn
@@ -24,6 +24,9 @@
   link_target_type = "shared_library"
 }
 target(link_target_type, "libc++") {
+  if (!libcpp_is_static) {
+    no_default_deps = true
+  }
   sources = [
     "trunk/src/algorithm.cpp",
     "trunk/src/any.cpp",