cargo-test: do not run dnf install if no dev deps

Signed-off-by: Igor Gnatenko <ignatenkobrain@fedoraproject.org>

cargo-test/runtest.sh

@@ -21,7 +21,7 @@ crate_toml="$crate_dir/Cargo.toml"
 # XXX: ideally we should just install -tests subpackage
 # which would require all necessary deps
 $(rpm --eval "%{__cargo_inspector}") --test-requires "$crate_toml" | \
-  sed -r -e "s/(.*)/'\1'/" | xargs sudo dnf -y install
+  sed -r -e "s/(.*)/'\1'/" | xargs -r sudo dnf -y install
 
 # XXX: sed is needed due to https://github.com/rpm-software-management/rpm/issues/472
 rpm -D "_with_check 1" --eval "%cargo_prep" | \