document include in bootstrap.example.toml

Signed-off-by: onur-ozkan <[email protected]>

Author: onur-ozkan

Diff for: bootstrap.example.toml

@@ -19,6 +19,11 @@
 # Note that this has no default value (x.py uses the defaults in `bootstrap.example.toml`).
 #profile = <none>
 
+# Inherits configuration values from different configuration files (a.k.a. config extensions).
+# Supports absolute paths, and uses the current directory (where the bootstrap was invoked)
+# as the base if the given path is not absolute.
+#include = []
+
 # Keeps track of major changes made to this configuration.
 #
 # This value also represents ID of the PR that caused major changes. Meaning,

Diff for: src/doc/rustc-dev-guide/src/building/suggested.md

@@ -53,8 +53,9 @@ include = ["cross.toml"]
 
 You can also include extensions within extensions recursively.
 
-**Note:** In the `include` field, the overriding logic follows a right-to-left order. Also, the outer
-extension/config always overrides the inner ones.
+**Note:** In the `include` field, the overriding logic follows a right-to-left order. For example,
+in `include = ["a.toml", "b.toml"]`, extension `b.toml` overrides `a.toml`. Also, parent extensions
+always overrides the inner ones.
 
 ## Configuring `rust-analyzer` for `rustc`