rust: cargo fixes for out of tree build

rust/Cargo.toml.in

@@ -4,6 +4,7 @@ version = "@PACKAGE_VERSION@"
 
 [lib]
 crate-type = ["staticlib"]
+path = "@abs_srcdir@/src/lib.rs"
 
 [profile.release]
 debug = true

rust/Makefile.am

@@ -31,31 +31,25 @@ endif
 
 all-local:
 if HAVE_PYTHON
-	cd $(top_srcdir)/rust && \
-		$(HAVE_PYTHON) ./gen-c-headers.py && \
-		CARGO_TARGET_DIR=$(abs_builddir)/target \
-		CARGO_HOME=$(CARGO_HOME) $(CARGO) build $(RELEASE) $(FROZEN) \
-			--features "$(RUST_FEATURES)"
+	cd $(top_srcdir)/rust && $(HAVE_PYTHON) ./gen-c-headers.py
+	CARGO_HOME=$(CARGO_HOME) $(CARGO) build $(RELEASE) $(FROZEN) \
+		--features "$(RUST_FEATURES)"
 else
-	cd $(top_srcdir)/rust && CARGO_TARGET_DIR=$(abs_builddir)/target \
-		CARGO_HOME=$(CARGO_HOME) $(CARGO) build $(RELEASE) $(FROZEN) \
-			--features "$(RUST_FEATURES)"
+	CARGO_HOME=$(CARGO_HOME) $(CARGO) build $(RELEASE) $(FROZEN) \
+		--features "$(RUST_FEATURES)"
 endif
 
 clean-local:
-	cd $(top_srcdir)/rust && CARGO_TARGET_DIR=$(abs_builddir)/target \
-		CARGO_HOME=$(CARGO_HOME) $(CARGO) clean
+	-rm -rf target
 
-distclean-local:
+distclean-local: clean-local
 	rm -rf vendor gen Cargo.lock
 
 check:
-	cd $(top_srcdir)/rust && CARGO_TARGET_DIR=$(abs_builddir)/target \
-		CARGO_HOME=$(CARGO_HOME) $(CARGO) test
+	CARGO_HOME=$(CARGO_HOME) $(CARGO) test
 
 Cargo.lock: Cargo.toml
-	cd $(top_srcdir)/rust && \
-		CARGO_HOME=$(CARGO_HOME) $(CARGO) generate-lockfile
+	CARGO_HOME=$(CARGO_HOME) $(CARGO) generate-lockfile
 
 if HAVE_CARGO_VENDOR
 vendor: