update readme

README.md

@@ -127,6 +127,56 @@ $ grep ^ .git/modules/*/HEAD .git/HEAD
 .git/HEAD:ref: refs/heads/proton_3.16
 ```
 
+## Sanity checks
+
+- check there are no 64-bit libs under ``dist/dist/lib/``
+  nor 32-bit libs under ``dist/dist/lib64/``.
+  This can happen when having issues with the Makefiles,
+  e.g. unset ``FFMPEG_CROSS_LDFLAGS := -m32`` in ``build/makefile_base.mak``
+  if building ``--with-ffmpeg``:
+
+  ```
+  user@proton:~/proton$ find dist/dist/lib/ -xdev -type f -exec sh -c "file '{}' | grep -vE 'ASCII|MS-DOS executable|PE32 executable|ELF 32-bit'" \;
+  user@proton:~/proton$ find dist/dist/lib64/ -xdev -type f -exec sh -c "file '{}' | grep -vE 'ASCII|MS-DOS executable|PE32\+ executable|ELF 64-bit'" \;
+  ```
+
+- check ffmpeg (if built with ``--with-ffmpeg``)
+  
+  ```
+  ls -la dist/dist/lib{,64}/lib{avcodec,avutil,swresample}*
+  ```
+
+- check xaudio2 (FAudio)
+  
+  ```
+  ls -la dist/dist/lib{,64}/libFAudio.so
+  ls -la dist/dist/lib{,64}/wine/x3daudio1_{0..7}.dll.so
+  ls -la dist/dist/lib{,64}/wine/xactengine3_{0..7}.dll.so
+  ls -la dist/dist/lib{,64}/wine/xapofx1_{1..5}.dll.so
+  ls -la dist/dist/lib{,64}/wine/xaudio2_{0..9}.dll.so
+  ```
+  
+  > If ``xactengine3`` is missing then apply https://github.com/ValveSoftware/wine/commit/e0e3165c15, https://github.com/ValveSoftware/wine/commit/967f095438
+
+- check DXVK
+  
+  ```
+  ls -la dist/dist/lib{,64}/wine/dxvk/*dll
+  ```
+
+- check lsteamclient
+  
+  ```
+  ls -la dist/dist/lib{,64}/wine/lsteamclient.dll.so
+  ```
+
+- check vrclient
+  
+  ```
+  ls -la dist/dist/{lib/wine/vrclient.dll.so,lib64/wine/vrclient_x64.dll.so}
+  ls -la dist/dist/{lib/wine/fakedlls/vrclient.dll,lib64/wine/fakedlls/vrclient_x64.dll}
+  ```
+
 ## Ccache
 
 > ccache is a compiler cache. It speeds up recompilation by caching previous