treewide: migrate to toolchain_cc

This contains the first part of the toolchain_cc migration. It leaves
the native host GCC, but everything that we ship is now built with
toolchain_cc with the exception of Linux which gets migrated later in
this stack.

Change-Id: Icb3422857fd3baf0ff61b7edd5754517f6a73dfc
Reviewed-on: https://review.monogon.dev/c/monogon/+/4012
Tested-by: Jenkins CI
Reviewed-by: Tim Windelschmidt <tim@monogon.tech>
diff --git a/build/toolchain/BUILD.bazel b/build/toolchain/BUILD.bazel
index 75cd911..a1d2288 100644
--- a/build/toolchain/BUILD.bazel
+++ b/build/toolchain/BUILD.bazel
@@ -51,7 +51,7 @@
 
 config_setting(
     name = "is_dynamic",
-    flag_values = {"//build/platforms/linkmode:static": "False"},
+    flag_values = {"@toolchain_cc_mngn//buildmode:static": "False"},
 )
 
 toolchain(