[docs] Explain how to update local cemu repo + General fixes (#227)

Co-authored-by: Crementif <26669564+Crementif@users.noreply.github.com>

BUILD.md

@@ -12,11 +12,11 @@ Instructions:
 
 1. Run `git clone --recursive https://github.com/cemu-project/Cemu`
 2. Launch `Cemu/generate_vs_solution.bat`.
-    - If you installed VS to a custom location or use VS 2019, you may need to manually change the path inside the .bat file
+    - If you installed VS to a custom location or use VS 2019, you may need to manually change the path inside the .bat file.
-3. Wait until it's done, then open `Cemu/build/Cemu.sln` in Visual Studio
+3. Wait until it's done, then open `Cemu/build/Cemu.sln` in Visual Studio.
 4. Then build the solution and once finished you can run and debug it, or build it and check the /bin folder for the final Cemu_release.exe.
 
-You can also skip steps 3-5 and open the root folder of the cloned repo directly in Visual Studio (as a folder) and use the built-in cmake support but be warned that cmake support in VS can be a bit finicky.
+You can also skip steps 3-5 and open the root folder of the cloned repo directly in Visual Studio (as a folder) and use the built-in CMake support but be warned that cmake support in VS can be a bit finicky.
 
 ## Linux
 
@@ -26,13 +26,14 @@ To compile Cemu, a recent enough compiler and STL with C++20 support is required
 
 #### For Ubuntu and derivatives:
 `sudo apt install -y git curl cmake ninja-build nasm libgtk-3-dev libsecret-1-dev libgcrypt20-dev libsystemd-dev freeglut3-dev libpulse-dev` 
-Additionally, for ubuntu 20.04 only:
+
+*Additionally, for Ubuntu 22.04 only:*
  - `sudo apt install -y clang-12`
  - At step 3 while building, use  
    `cmake -S . -B build -DCMAKE_BUILD_TYPE=release -DCMAKE_C_COMPILER=/usr/bin/clang-12 -DCMAKE_CXX_COMPILER=/usr/bin/clang++-12 -G Ninja -DCMAKE_MAKE_PROGRAM=/usr/bin/ninja`
 
 #### For Arch and derivatives:
-`sudo pacman -S git cmake clang ninja nasm base-devel linux-headers gtk3 libsecret libgcrypt systemd freeglut zip libpulse`
+`sudo pacman -S git cmake clang ninja nasm base-devel linux-headers gtk3 libsecret libgcrypt systemd freeglut zip unzip libpulse`
 
 #### For Fedora and derivatives:
 `sudo dnf install git cmake clang ninja-build nasm kernel-headers gtk3-devel libsecret-devel libgcrypt-devel systemd-devel freeglut-devel perl-core zlib-devel cubeb-devel`
@@ -56,4 +57,11 @@ You can use it by replacing the step 3 with the following:
  - If step 3 is still failing or if you're not able to find the cause, please make an issue on our Github about it!
  - If step 4 gives you an error that contains something like `main.cpp.o: in function 'std::__cxx11::basic_string...`, you likely are experiencing a clang-14 issue. This can only be fixed by either lowering the clang version or using GCC, see below.
  - If step 4 gives you a different error, you could report it to this repo or try using GCC. Just make sure your standard library and compilers are updated since Cemu uses a lot of modern features!
-- If step 4 gives you undefined libdecor_xx, you are likely experiencing an issue with sdl2 package that comes with vcpkg. Delete sdl2 from vcpkg.json in source file and recompile
+- If step 4 gives you undefined libdecor_xx, you are likely experiencing an issue with sdl2 package that comes with vcpkg. Delete sdl2 from vcpkg.json in source file and recompile.
+
+## Updating Cemu and source code
+1. To update your Cemu local repository, use the command `git pull --recurse-submodules` (run this command on the Cemu root).
+    - This should update your local copy of Cemu and all of its dependencies.
+2. Then, you can rebuild Cemu using the steps listed above, according to whether you use Linux or Windows.
+
+If CMake complains about Cemu already being compiled or another similar error, try deleting the `CMakeCache.txt` file inside the `build` folder and retry building.