Preserve existing behavior with removing build dir

Signed-off-by: Ryan Friedman <ryanfriedman5410+github@gmail.com>

CONTRIBUTING.md

@@ -68,7 +68,7 @@ Once you have a GitHub login:
 
 5. Configure the project and check that it builds (if not, please report a bug):
 
-        $ rm -r build
+        $ rm -rf build
         $ cmake -S . -B build -DCMAKE_BUILD_TYPE=Release
         $ cmake --build build --parallel
 

README.md

@@ -82,7 +82,6 @@ You need [CMake](https://cmake.org/download/) to configure the Exiv2 project, an
 
 ```bash
 $ cd ~/gnu/github/exiv2                          # Location of the project code
-$ rm -r build                                    # Remove existing build directory
 $ cmake -S . -B build -DCMAKE_BUILD_TYPE=Release # Configure the project with CMake
 $ cmake --build build                            # Compile the project
 $ ctest --test-dir build --verbose               # Run tests