Update CONTRIBUTING.md and README.md

Signed-off-by: Bensuperpc <bensuperpc@gmail.com>

CONTRIBUTING.md

@@ -189,7 +189,7 @@ Once this part is finished, there must be 3 files in the **linux-arm64** folder:
 - **Dockerfile.in**, the docker file.
 - **Toolchain.cmake**, the CMake file for the toolchains.
 
-### Makefile and CI
+### Makefile
 
 For this last part, we will see how to add the image to the [Makefile](Makefile) and to a github action.
 
@@ -225,6 +225,42 @@ GEN_IMAGES = android-arm android-arm64 \
  linux-riscv64 linux-riscv32 linux-m68k-uclibc linux-x64-tinycc linux-xtensa-uclibc
 ```
 
+### Image building and testing
+
+You can now start building the image:
+
+```bash
+make linux-arm64
+```
+
+When finished, you can test it:
+
+```bash
+make linux-arm64.test
+```
+
+If you want to go a little further in the tests:
+
+```bash
+docker run --rm linux-arm64 > ./linux-arm64
+chmod +x ./linux-arm64
+```
+
+And then run the commands to build a project (you must be in the directory of your project to build):
+
+```bash
+./linux-arm64 make
+```
+
+With CMake + Ninja:
+
+```bash
+./linux-arm64 cmake -Bbuild -S. -GNinja
+./linux-arm64 ninja -Cbuild
+```
+
+### CI (github action)
+
 To finish, you have to add to [Github Action](.github/workflows/main.yml) the image/folder name:
 
 ```yml

README.md

@@ -25,7 +25,7 @@ Cross compiling toolchains in Docker images.
 ## Examples
 
 1. `dockcross make`: Build the *Makefile* in the current directory.
-2. `dockcross cmake -Bbuild -H. -GNinja`: Run CMake with a build directory `./build` for a *CMakeLists.txt* file in the current directory and generate `ninja` build configuration files.
+2. `dockcross cmake -Bbuild -S. -GNinja`: Run CMake with a build directory `./build` for a *CMakeLists.txt* file in the current directory and generate `ninja` build configuration files.
 3. `dockcross ninja -Cbuild`: Run ninja in the `./build` directory.
 4. `dockcross bash -c '$CC test/C/hello.c -o hello'`: Build the *hello.c* file with the compiler identified with the `CC` environmental variable in the build environment.
 5. `dockcross bash`: Run an interactive shell in the build environment.