Document build.build-requires feature

Signed-off-by: Cristian Le <[email protected]>

Author: LecrisUT

Diff for: docs/configuration.md

@@ -649,6 +649,47 @@ Support for `result` and `remove` added.
 
 :::
 
+:::{tab} build-requires
+
+```{versionadded} 0.11
+
+```
+
+If you need to inject and manipulate additional `build-system.requires`, you can
+use the `build.build-requires`. This is intended to be used in combination with
+[](./overrides.md).
+
+This is not technically a dynamic metadata and thus does not have to have the
+`dynamic` field defined, and it is not defined under the `metadata` table, but
+similar to the other dynamic metadata it injects the additional
+`build-system.requires`.
+
+```toml
+[package]
+name = "mypackage"
+
+[tool.scikit-build.build]
+build-requires = ["foo"]
+
+[[tool.scikit-build.overrides]]
+if.from-sdist = false
+build.build-requires = ["foo @ {root:uri}/foo"]
+```
+
+This example shows a common use-case where the package has a default
+`build-system.requires` pointing to the package `foo` in the PyPI index, but
+when built from the original git checkout or equivalent, the local folder is
+used as dependency instead by resolving the `{root:uri}` to a file uri pointing
+to the folder where the `pyproject.toml` is located.
+
+```{note}
+In order to be compliant with the package index, when building from `sdist`, the
+`build.build-requires` **MUST NOT** have any `@` redirects. This rule may be later
+enforced explicitly.
+```
+
+:::
+
 :::{warning}
 
 Your package and third-party packages can also extend these with new plugins,