Let specify arbitrary build configuration via Docker

Default to RelWithDebInfo for both optimizations and debug information

.github/workflows/linux.yml

@@ -85,7 +85,7 @@ jobs:
 
           docker run --rm \
           -v $PWD:/usr/src/tdesktop \
-          -e DEBUG=1 \
+          -e CONFIG=Debug \
           tdesktop:centos_env \
           /usr/src/tdesktop/Telegram/build/docker/centos_env/build.sh \
           -D CMAKE_C_FLAGS_DEBUG="" \

Telegram/build/docker/centos_env/build.sh

@@ -3,9 +3,4 @@ set -e
 
 cd Telegram
 ./configure.sh "$@"
-
-if [ -n "$DEBUG" ]; then
-	cmake --build ../out --config Debug --parallel
-else
-	cmake --build ../out --config Release --parallel
-fi
+cmake --build ../out --config "${CONFIG:-RelWithDebInfo}" --parallel

docs/building-linux.md

@@ -30,7 +30,7 @@ Or, to create a debug build, run (also using [your **api_id** and **api_hash**](
 
     docker run --rm -it \
         -v $PWD:/usr/src/tdesktop \
-        -e DEBUG=1 \
+        -e CONFIG=Debug \
         tdesktop:centos_env \
         /usr/src/tdesktop/Telegram/build/docker/centos_env/build.sh \
         -D TDESKTOP_API_ID=YOUR_API_ID \