Building_Linux.md: Use `cmake -S ../vcmi` instead of `cmake ../vcmi`

docs/developers/Building_Linux.md

@@ -49,12 +49,14 @@ Information about building packages from the Arch User Repository (AUR) can be f
 
 # Getting the sources
 
-VCMI is still in development. We recommend the following initial directory structure:
+We recommend the following directory structure:
 
     .
     ├── vcmi -> contains sources and is under git control
     └── build -> contains build output, makefiles, object files,...
 
+Out-of-source builds keep the local repository clean so one doesn't have to manually exclude files generated during the build from commits.
+
 You can get latest sources with:
 
 `git clone -b develop --recursive https://github.com/vcmi/vcmi.git`
@@ -65,25 +67,25 @@ You can get latest sources with:
 
 ```sh
 mkdir build && cd build
-cmake ../vcmi
+cmake -S ../vcmi
 ```
 
 # Additional options that you may want to use:
 
 ## To enable debugging:
-`cmake ../vcmi -D CMAKE_BUILD_TYPE=Debug`
+`cmake -S ../vcmi -D CMAKE_BUILD_TYPE=Debug`
 
 **Notice**: The ../vcmi/ is not a typo, it will place makefile scripts into the build dir as the build dir is your working dir when calling CMake.
 
 ## To use ccache:
-`cmake ../vcmi -D ENABLE_CCACHE:BOOL=ON`
+`cmake -S ../vcmi -D ENABLE_CCACHE:BOOL=ON`
 
 ## Trigger build
 
 `cmake --build . -- -j2`
 (-j2 = compile with 2 threads, you can specify any value)
 
-That will generate vcmiclient, vcmiserver, vcmilauncher as well as .so libraries in **build/bin/** directory.
+That will generate vcmiclient, vcmiserver, vcmilauncher as well as .so libraries in the **build/bin/** directory.
 
 # Package building