rustPlatform.maturinBuildHook: specify the output directory (#291025)

pkgs/build-support/rust/hooks/maturin-build-hook.sh

···
 
     runHook preBuild
 
+    # Put the wheel to dist/ so that regular Python tooling can find it.
+    local dist="$PWD/dist"
+
     if [ ! -z "${buildAndTestSubdir-}" ]; then
         pushd "${buildAndTestSubdir}"
     fi
···
         --manylinux off \
         --strip \
         --release \
+        --out "$dist" \
         ${maturinBuildFlags-}
     )
 
     if [ ! -z "${buildAndTestSubdir-}" ]; then
         popd
     fi
-
-    # Move the wheel to dist/ so that regular Python tooling can find it.
-    mkdir -p dist
-    mv ${cargoRoot:+$cargoRoot/}target/wheels/*.whl dist/
 
     # These are python build hooks and may depend on ./dist
     runHook postBuild