Fix cargo cross compilation [skip ci]

Author: Claudio Raimondi

Dockerfile

@@ -118,7 +118,7 @@ ENV LIGHTNINGD_VERSION=master
 
 RUN dpkg --add-architecture ${target_arch_dpkg}
 
-#TODO: python3-dev needs QEMU for post install scripts. find a workaround
+#TODO: python3-dev needs QEMU for post install scripts. find a workaround to not use QEMU
 RUN apt-get update && \
     apt-get install -qq -y --no-install-recommends \
         pkg-config:${target_arch_dpkg} \
@@ -139,7 +139,7 @@ ARG TARGET=${target_arch_rust}
 ARG COPTFLAGS="-O2 ${COPTFLAGS}"
 ARG RUST_PROFILE=release
 
-#TODO: set via env
+#TODO: set all these config options via env variables (https://doc.rust-lang.org/cargo/reference/environment-variables.html)
 RUN mkdir -p .cargo && tee .cargo/config.toml <<EOF
 
 [build]
@@ -165,7 +165,6 @@ RUN git submodule update --init --recursive --jobs $(nproc) --depth 1
 
 #TODO: Fix unaligned access on armv7
 RUN ./configure --prefix=/tmp/lightning_install --enable-static --disable-compat --disable-valgrind
-#TODO: Fix cp stat error on amd64 x86-64
 RUN uv run make install-program -j$(nproc)
 
 RUN find /tmp/lightning_install -type f -executable -exec \

Makefile

@@ -345,6 +345,14 @@ endif
 	fi
 
 RUST_PROFILE ?= debug
+
+# Cargo places cross compiled packages in a different directory, using the target triple
+ifeq ($(TARGET),)
+RUST_TARGET_DIR = target/$(RUST_PROFILE)
+else
+RUST_TARGET_DIR = target/$(TARGET)/$(RUST_PROFILE)
+endif
+
 ifneq ($(RUST_PROFILE),debug)
 CARGO_OPTS := --profile=$(RUST_PROFILE) --quiet
 else