sim: Move csupport into mcuboot-sys

This C code is also part of the binding.  Move it into the binding crate
to reflect this.

Signed-off-by: David Brown <david.brown@linaro.org>
diff --git a/sim/mcuboot-sys/build.rs b/sim/mcuboot-sys/build.rs
index 4f4cf9e..1b3c7d4 100644
--- a/sim/mcuboot-sys/build.rs
+++ b/sim/mcuboot-sys/build.rs
@@ -55,7 +55,7 @@
     conf.file("../../boot/bootutil/src/loader.c");
     conf.file("../../boot/bootutil/src/caps.c");
     conf.file("../../boot/bootutil/src/bootutil_misc.c");
-    conf.file("../csupport/run.c");
+    conf.file("csupport/run.c");
     conf.include("../../boot/bootutil/include");
     conf.include("../../boot/zephyr/include");
     conf.debug(true);
@@ -64,7 +64,7 @@
     conf.compile("libbootutil.a");
 
     walk_dir("../../boot").unwrap();
-    walk_dir("../csupport").unwrap();
+    walk_dir("csupport").unwrap();
     walk_dir("mbedtls/include").unwrap();
     walk_dir("mbedtls/library").unwrap();
 }