Add C to Rust example

c-to-rust/Makefile

@@ -0,0 +1,18 @@
+all: target/double
+	target/double
+
+target:
+	mkdir -p $@
+
+target/double: target/main.o target/libdouble_input.a
+	$(CC) -o $@ -Wl,--gc-sections $^ -lpthread
+
+target/libdouble_input.a: src/lib.rs Cargo.toml
+	cargo build
+	(cd target && ln -nsf debug/libdouble_input-*.a libdouble_input.a)
+
+target/main.o: src/main.c | target
+	$(CC) -o $@ -c $<
+
+clean:
+	rm -rf target