rust: Avoid requiring development dependencies

Cargo will always require all depenendencies, even if the package is not
being built against them. In order to avoid that, we will need the
nightly build of the Rust compiler which supports skipping those
dependencies.

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>

lfs/Config

@@ -184,7 +184,13 @@ export CARGO_CONFIG
 
 CARGO = \
 	CARGOPATH=$(CARGO_PATH) \
-	cargo
+	RUSTC_BOOTSTRAP=1 \
+	cargo \
+	--offline
+
+CARGO_OPTIONS = \
+	$(MAKETUNING) \
+	-Z avoid-dev-deps
 
 define CARGO_PREPARE
 	mkdir -p $(CARGO_PATH) && \
@@ -195,11 +201,11 @@ endef
 CARGO_BUILD = \
 	$(CARGO) \
 	build \
-	$(MAKETUNING) \
-	--release
+	--release \
+	$(CARGO_OPTIONS)
 
 # Checks whether this crate has a right taregt
-CARGO_TARGET_CHECK = cargo metadata --format-version 1 | \
+CARGO_TARGET_CHECK = $(CARGO) metadata --format-version 1 --no-deps | \
 	jq -e ".packages[].targets[].kind | any(. == \"$(1)\")" | grep -q "true"
 
 define CARGO_INSTALL
@@ -214,7 +220,7 @@ define CARGO_INSTALL
 		echo "{\"files\":{},\"package\":\"\"}" > $(CRATE_PATH)/.cargo-checksum.json; \
 	fi && \
 	if $(call CARGO_TARGET_CHECK,bin); then \
-		$(CARGO) install --no-track --path .; \
+		$(CARGO) install $(CARGO_OPTIONS) --no-track --path .; \
 	fi
 endef