Update docs/docker to use FFmpeg 4.2 / OpenAL 1.20.1.

docs/building-cmake.md

@@ -1,5 +1,7 @@
 ## Build instructions for CMake under Ubuntu 14.04
 
+**NB** These are outdated.
+
 ### Prepare folder
 
 Choose an empty folder for the future build, for example **/home/user/TBuild**. It will be named ***BuildPath*** in the rest of this document.

docs/building-msvc.md

@@ -152,7 +152,7 @@ Open **x86 Native Tools Command Prompt for VS 2019.bat**, go to ***BuildPath***
 
     git clone https://github.com/FFmpeg/FFmpeg.git ffmpeg
     cd ffmpeg
-    git checkout release/3.4
+    git checkout release/4.2
 
     set CHERE_INVOKING=enabled_from_arguments
     set MSYS2_PATH_TYPE=inherit
@@ -172,7 +172,7 @@ Open **x86 Native Tools Command Prompt for VS 2019.bat**, go to ***BuildPath***
     cd ..
 
     configure ^
-        -prefix "%LibrariesPath%\Qt-Qt-5.15.1" ^
+        -prefix "%LibrariesPath%\Qt-5.15.1" ^
         -debug-and-release ^
         -force-debug-info ^
         -opensource ^

docs/building-xcode.md

@@ -127,7 +127,7 @@ Go to ***BuildPath*** and run
 
     git clone https://github.com/FFmpeg/FFmpeg.git ffmpeg
     cd ffmpeg
-    git checkout release/3.4
+    git checkout release/4.2
     CFLAGS=`freetype-config --cflags`
     LDFLAGS=`freetype-config --libs`
     PKG_CONFIG_PATH=$PKG_CONFIG_PATH:/usr/local/lib/pkgconfig:/usr/lib/pkgconfig:/usr/X11/lib/pkgconfig
@@ -240,9 +240,9 @@ Go to ***BuildPath*** and run
     sudo make install
     cd ..
 
-    git clone git://repo.or.cz/openal-soft.git
+    git clone https://github.com/telegramdesktop/openal-soft.git
     cd openal-soft
-    git checkout v1.19
+    git checkout fix_mono
     cd build
     CFLAGS=$UNGUARDED CPPFLAGS=$UNGUARDED cmake -D CMAKE_INSTALL_PREFIX:PATH=/usr/local/macos -D ALSOFT_EXAMPLES=OFF -D LIBTYPE:STRING=STATIC -D CMAKE_OSX_DEPLOYMENT_TARGET:STRING=10.12 ..
     make $MAKE_THREADS_CNT