Further clarify cert error message on Windows

Summary:
As title, we've gotten quite a few reports on Windows Users group (see [post](https://fb.workplace.com/groups/winbook/permalink/3907943359478714/)) from this message.
Based on the comments users are running the `getchef` command on a non-admin terminal which doesn't fix their issue.
Here I'm modifying the error to explicitly mention they should run this on an admin PowerShell.

I know this seems pretty hacky, but wanted to start a discussion on whether this is good and get suggestions if this is plain bad :D

Reviewed By: JakobDegen

Differential Revision: D75090979

fbshipit-source-id: b20605b7a891fb63ac33253731ab42b088796f82

Author: Luis Regino Hernández

app/buck2_certs/src/certs.rs

@@ -25,12 +25,19 @@ async fn load_system_root_certs() -> buck2_error::Result<RootCertStore> {
     let native_certs =
         rustls_native_certs::load_native_certs().tag(buck2_error::ErrorTag::Environment);
     let native_certs = if cfg!(fbcode_build) {
-        native_certs.buck_error_context(
+        let windows_message = if cfg!(target_os = "windows") {
+            " on an admin PowerShell"
+        } else {
+            ""
+        };
+        let context = format!(
             "Error loading system root certificates native frameworks.
             This is usually due to Chef not installed or working properly.
-            Please try `getchef -reason 'chef broken'`, `Fix My <OS>` via the f-menu, then `buck2 killall`.
+            Please try `getchef -reason 'chef broken'`{}, `Fix My <OS>` via the f-menu, then `buck2 killall`.
             If that doesn't resolve it, please visit HelpDesk to get Chef back to a healthy state.",
-        )
+            windows_message
+        );
+        native_certs.buck_error_context(context)
     } else {
         native_certs.buck_error_context("Error loading system root certificates native frameworks.")
     };