`@bazel_tool//tools/cpp:link_extra_libs` should not propagate to exec config

### Description of the feature request:

The C++ compilation rules have a neat feature: they [allow you](https://bazel.build/reference/be/c-cpp#cc_binary.link_extra_lib) to specify a library that should be a linktime dependency of all `cc_binary` targets. That library is configured through a label flag, `@bazel_tool//tools/cpp:link_extra_libs`.

Unfortunately, this label flag persists across the transition from the target to the exec configuration. This is very inconvenient: if the `link_extra_libs` you want for the target platform include generated code, you run into circular dependencies when trying to build any binaries used in their generation. This tends to happen with [some Pigweed libraries](https://pigweed.dev/build_system.html#docs-build-system-bazel-link-extra-lib), preventing us from using `link_extra_libs` in most cases.

@gregestren I recall that internally we've done some work to restrict flag propagation to the exec config (b/292617118). What's the status on the open source side?

### Which category does this issue belong to?

Configurability

### What underlying problem are you trying to solve with this feature?

_No response_

### Which operating system are you running Bazel on?

_No response_

### What is the output of `bazel info release`?

release 7.1.2

### If `bazel info release` returns `development version` or `(@non-git)`, tell us how you built Bazel.

_No response_

### What's the output of `git remote get-url origin; git rev-parse HEAD` ?

_No response_

### Have you found anything relevant by searching the web?

_No response_

### Any other information, logs, or outputs that you want to share?

_No response_