ninjabackend: add support for "ninja clippy"

Add a target that builds all crates that could be extern to others,
and then reruns clippy.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 20 insertions, 0 deletions

diff --git a/docs/markdown/howtox.md b/docs/markdown/howtox.md
index 4a57e8569..ba6a3b8f8 100644
--- a/docs/markdown/howtox.md
+++ b/docs/markdown/howtox.md
@@ -239,6 +239,26 @@ And then pass it through the variable (remember to use absolute path):
 $ SCANBUILD=$(pwd)/my-scan-build.sh ninja -C builddir scan-build
 ```
 
+## Use clippy
+
+If your project includes Rust targets, you can invoke clippy like this:
+
+```console
+$ meson setup builddir
+$ ninja -C builddir clippy
+```
+
+Clippy will also obey the `werror` [builtin option](Builtin-options.md#core-options).
+
+By default Meson uses as many concurrent processes as there are cores
+on the test machine. You can override this with the environment
+variable `MESON_NUM_PROCESSES`.
+
+Meson will look for `clippy-driver` in the same directory as `rustc`,
+or try to invoke it using `rustup` if `rustc` points to a `rustup`
+binary.  If `clippy-driver` is not detected properly, you can add it to
+a [machine file](Machine-files.md).
+
 ## Use profile guided optimization
 
 Using profile guided optimization with GCC is a two phase