[CI] run-make/thumb: tidy up variables

Author: sekineh

src/test/run-make/thumb-none-cortex-m/Makefile

@@ -1,23 +1,25 @@
 -include ../../run-make-fulldeps/tools.mk
 
 # How to run this
-# $ ./x.py dist --target x86_64-unknown-linux-gnu,thumbv7m-none-eabi --exclude src/doc
 # $ ./x.py test --target thumbv7m-none-eabi src/test/run-make
 
 ifeq ($(TARGET),thumbv7m-none-eabi)
 
-#TMP_DIR := $(shell mktemp -d)
-TMP_DIR := /tmp/safe_place
+# We need to be outside of 'src' dir in order to run cargo
+WORK_DIR := $(RUST_TEST_TMPDIR)/run-make/$(TARGET)
+
 CRATE := cortex-m
+CRATE_VER := 0.5.0
+
 RUSTC := $(RUSTC_ORIGINAL)
 LD_LIBRARY_PATH := $(HOST_RPATH_DIR)
 
 all:
-	env > env.txt
-	mkdir -p $(TMP_DIR)
-	-cd $(TMP_DIR) && rm -rf $(CRATE)
-	cd $(TMP_DIR) && $(CARGO) clone $(CRATE) --vers 0.5.0
-	cd $(TMP_DIR) && cd $(CRATE) && $(CARGO) build -j 1 --target $(TARGET) -v
+	env
+	mkdir -p $(WORK_DIR)
+	-cd $(WORK_DIR) && rm -rf $(CRATE)
+	cd $(WORK_DIR) && $(CARGO) clone $(CRATE) --vers $(CRATE_VER)
+	cd $(WORK_DIR) && cd $(CRATE) && $(CARGO) build -j 1 --target $(TARGET) -v
 else
 
 all: