diff --git a/artiq/firmware/bootloader/Makefile b/artiq/firmware/bootloader/Makefile
index 482aa3291..4dbd7b608 100644
--- a/artiq/firmware/bootloader/Makefile
+++ b/artiq/firmware/bootloader/Makefile
@@ -3,11 +3,15 @@ include $(MISOC_DIRECTORY)/software/common.mak
 
 RUSTFLAGS += -Cpanic=abort
 
+export XBUILD_SYSROOT_PATH=$(BUILDINC_DIRECTORY)/../sysroot
+
 all:: bootloader.bin
 
 .PHONY: $(RUSTOUT)/libbootloader.a
 $(RUSTOUT)/libbootloader.a:
-	$(cargo) --manifest-path $(BOOTLOADER_DIRECTORY)/Cargo.toml
+	$(cargo) --target-dir ./cargo \
+	--manifest-path $(BOOTLOADER_DIRECTORY)/Cargo.toml \
+	--target $(BOOTLOADER_DIRECTORY)/../riscv32ima-unknown-none-elf.json
 
 bootloader.elf: $(RUSTOUT)/libbootloader.a
 	$(link) -T $(BOOTLOADER_DIRECTORY)/bootloader.ld
diff --git a/artiq/firmware/ksupport/Makefile b/artiq/firmware/ksupport/Makefile
index cfb79b3d6..f1fbfc19a 100644
--- a/artiq/firmware/ksupport/Makefile
+++ b/artiq/firmware/ksupport/Makefile
@@ -14,11 +14,15 @@ LDFLAGS += --eh-frame-hdr \
 
 RUSTFLAGS += -Cpanic=unwind
 
+export XBUILD_SYSROOT_PATH=$(BUILDINC_DIRECTORY)/../sysroot
+
 all:: ksupport.elf
 
 .PHONY: $(RUSTOUT)/libksupport.a
 $(RUSTOUT)/libksupport.a:
-	$(cargo) --manifest-path $(KSUPPORT_DIRECTORY)/Cargo.toml
+	$(cargo) --target-dir ./cargo \
+	--manifest-path $(KSUPPORT_DIRECTORY)/Cargo.toml \
+	--target $(KSUPPORT_DIRECTORY)/../riscv32ima-unknown-none-elf.json
 
 ksupport.elf: $(RUSTOUT)/libksupport.a glue.o
 	$(link) -T $(KSUPPORT_DIRECTORY)/ksupport.ld \
diff --git a/artiq/firmware/runtime/Makefile b/artiq/firmware/runtime/Makefile
index 24ac19741..00506b2f3 100644
--- a/artiq/firmware/runtime/Makefile
+++ b/artiq/firmware/runtime/Makefile
@@ -10,11 +10,15 @@ LDFLAGS += \
 
 RUSTFLAGS += -Cpanic=unwind
 
+export XBUILD_SYSROOT_PATH=$(BUILDINC_DIRECTORY)/../sysroot
+
 all:: runtime.bin runtime.fbi
 
 .PHONY: $(RUSTOUT)/libruntime.a
 $(RUSTOUT)/libruntime.a:
-	$(cargo) --manifest-path $(RUNTIME_DIRECTORY)/Cargo.toml
+	$(cargo) --target-dir ./cargo \
+	--manifest-path $(RUNTIME_DIRECTORY)/Cargo.toml \
+	--target $(RUNTIME_DIRECTORY)/../riscv32ima-unknown-none-elf.json
 
 runtime.elf: $(RUSTOUT)/libruntime.a ksupport_data.o
 	$(link) -T $(RUNTIME_DIRECTORY)/runtime.ld \
diff --git a/artiq/firmware/satman/Makefile b/artiq/firmware/satman/Makefile
index 59f0f78f6..1f441c018 100644
--- a/artiq/firmware/satman/Makefile
+++ b/artiq/firmware/satman/Makefile
@@ -9,7 +9,9 @@ all:: satman.bin satman.fbi
 
 .PHONY: $(RUSTOUT)/libsatman.a
 $(RUSTOUT)/libsatman.a:
-	$(cargo) --manifest-path $(SATMAN_DIRECTORY)/Cargo.toml
+	$(cargo) --target-dir ./cargo \
+	--manifest-path $(SATMAN_DIRECTORY)/Cargo.toml \
+	--target $(SATMAN_DIRECTORY)/../riscv32ima-unknown-none-elf.json
 
 satman.elf: $(RUSTOUT)/libsatman.a
 	$(link) -T $(SATMAN_DIRECTORY)/satman.ld
diff --git a/flake.nix b/flake.nix
index dc192e57b..3ad177a03 100644
--- a/flake.nix
+++ b/flake.nix
@@ -180,6 +180,20 @@
           propagatedBuildInputs = with pkgs.python3Packages; [ jinja2 numpy migen pyserial asyncserial ];
         };
 
+        cargo-xbuild = rustPlatform.buildRustPackage rec {
+          pname = "cargo-xbuild";
+          version = "0.6.5";
+
+          src = pkgs.fetchFromGitHub {
+            owner = "rust-osdev";
+            repo = pname;
+            rev = "v${version}";
+            sha256 = "18djvygq9v8rmfchvi2hfj0i6fhn36m716vqndqnj56fiqviwxvf";
+          };
+
+          cargoSha256 = "13sj9j9kl6js75h9xq0yidxy63vixxm9q3f8jil6ymarml5wkhx8";
+        };
+
         vivadoEnv = pkgs.buildFHSUserEnv {
           name = "vivado-env";
           targetPkgs = vivadoDeps;
@@ -211,6 +225,7 @@
                 pkgs.lld_11
                 vivado
                 rustPlatform.cargoSetupHook
+                cargo-xbuild
               ];
               buildPhase = 
                 ''