pw_libc: Don't implicitly link against global link_deps

This added a lot of extra object files into pw_libc.a which
has `complete_static_lib = true`. This didn't cause any
problems because none of those symbols would have been
extracted from pw_libc.a (and if they were they wouldn't
be extracted later). Regardless, it is better that
pw_libc.a include only libc symbols.

Change-Id: I172b8b77b63e37760fc5d81b7795b2ab5aff42fd
Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/150051
Original-Reviewed-by: Petr Hosek <phosek@google.com>
Original-Reviewed-by: Armando Montanez <amontanez@google.com>
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/llvm-integration/+/235129
Reviewed-by: Armando Montanez <amontanez@google.com>
Commit-Queue: Prabhu Karthikeyan Rajasekaran <prabhukr@google.com>
Reviewed-by: Keir Mierle <keir@google.com>
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
diff --git a/pw_libc/BUILD.gn b/pw_libc/BUILD.gn
index b4b76e3..9f441e8 100644
--- a/pw_libc/BUILD.gn
+++ b/pw_libc/BUILD.gn
@@ -139,6 +139,7 @@
 
   pw_static_library("pw_libc") {
     complete_static_lib = true
+    add_global_link_deps = false
     deps = [
       ":ctype",
       ":math",
@@ -161,6 +162,7 @@
   }
 } else {
   pw_static_library("pw_libc") {
+    add_global_link_deps = false
   }
 
   pw_test_group("llvm_libc_tests") {