Fix: formating README's build

README.md

@@ -138,7 +138,7 @@ To mutate all of the `.cc` files in the library use the following command:
 ${DREDD_EXECUTABLE} -p build math/src/*.cc --mutation-info-file mutant-info.json
 ```
 
-The `-p` option allows the compilation database generated by CMake above to be passed to Dredd: the `compile_commands.json` file in build will be used as a compilation database.
+The `-p` option allows the compilation database generated by CMake above to be passed to Dredd: the `compile_commands.json` file in `build` will be used as a compilation database.
 This is so that Dredd knows the correct compiler options to use when processing each source file.
 
 You can run `git status` to see which files have changed, and `git diff` to see