cargo.bbclass: ensure extra RUSTFLAGS are properly passed

The RUSTFLAGS env var overrides the rustflags specified in the cargo
config so we need to take anything passed in the environment variable
and put it in the config.

classes/cargo.bbclass

@@ -54,7 +54,13 @@ EOF
 	# and uses HOST to be the currently selected one. However
 	# LDFLAGS and TOOLCHAIN_OPTIONS are not prefixed with HOST
 	echo "[build]" >> ${CARGO_HOME}/config
-    echo "rustflags = ['-C', 'link-args=${LDFLAGS}${HOST_CC_ARCH}${TOOLCHAIN_OPTIONS}']" >> ${CARGO_HOME}/config
+	echo "rustflags = [" >> ${CARGO_HOME}/config
+	echo "'-C'," >> ${CARGO_HOME}/config
+	echo "'link-args=${LDFLAGS}${HOST_CC_ARCH}${TOOLCHAIN_OPTIONS}'," >> ${CARGO_HOME}/config
+	for p in ${RUSTFLAGS}; do
+		printf "'%s'\n" "$p"
+	done | sed -e 's/$/,/' >> ${CARGO_HOME}/config
+	echo "]" >> ${CARGO_HOME}/config
 	echo "[target.${RUST_HOST_SYS}]" >> ${CARGO_HOME}/config
 	echo "linker = '${HOST_PREFIX}gcc'" >> ${CARGO_HOME}/config
 }
@@ -75,6 +81,7 @@ CARGO_BUILD_FLAGS = "-v --target ${HOST_SYS} --release"
 # change if CARGO_BUILD_FLAGS changes.
 CARGO_TARGET_SUBDIR="${HOST_SYS}/release"
 oe_cargo_build () {
+	unset RUSTFLAGS
 	bbnote "cargo = $(which cargo)"
 	bbnote "rustc = $(which rustc)"
 	bbnote "${CARGO} build ${CARGO_BUILD_FLAGS} $@"

recipes-devtools/cargo/cargo.inc

@@ -67,6 +67,10 @@ SRC_URI = "\
 
 B = "${S}"
 
+# Can't use the default from rust-vars as it cause a compiler crash
+# the crate_hash option will cause the compiler to crash
+RUSTFLAGS = "-C rpath ${RUSTLIB}"
+
 PACKAGECONFIG ??= ""
 
 # Note: this does not appear to work very well due to our use of bitbake triples