Updated README for current rustc

Author: kornelski

README.md

@@ -49,7 +49,7 @@ Build by running the following command:
 
 ```sh
 $ cargo rustc -- \
-    -C passes='sancov' \
+    -C passes='sancov-module' \
     -C llvm-args='-sanitizer-coverage-level=3' \
     -C llvm-args='-sanitizer-coverage-inline-8bit-counters' \
     -Z sanitizer=address