- ci: update to clang 10

versions before 9 fails to compile with the following error
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/bits/stl_tree.h:701:4: error: exception specification of explicitly defaulted move constructor does not match the calculated one

clang 9 fails to link with the following errors
/usr/bin/../lib/gcc/x86_64-linux-gnu/10/../../../../include/c++/10/cmath:223: undefined reference to `__expf_finite'
src/rendering/swrenderer/drawers/r_draw_rgba.cpp:1120: undefined reference to `__log2_finite'
src/rendering/swrenderer/drawers/r_draw_rgba.cpp:1120: undefined reference to `__log2_finite'
src/rendering/swrenderer/drawers/r_draw_rgba.cpp:1120: undefined reference to `__log2_finite'
src/rendering/swrenderer/plane/r_flatplane.cpp:183: undefined reference to `__log2_finite'
src/rendering/swrenderer/viewport/r_spritedrawer.cpp:174: undefined reference to `__log2_finite'

# Conflicts:
#	.github/workflows/continuous_integration.yml

.github/workflows/continuous_integration.yml

@@ -62,10 +62,10 @@ jobs:
             build_type: "MinSizeRel"
           }
         - {
-            name: "Linux Clang 6",
+            name: "Linux Clang 10",
             os: ubuntu-20.04,
-            extra_options: "-DCMAKE_C_COMPILER=clang-6.0 -DCMAKE_CXX_COMPILER=clang++-6.0 -DDYN_OPENAL=OFF",
-            deps_cmdline: "sudo apt update && sudo apt install clang-6.0 libsdl2-dev libvpx-dev libopenal-dev libfluidsynth-dev libmpg123-dev libsndfile1-dev",
+            extra_options: "-DCMAKE_C_COMPILER=clang-10 -DCMAKE_CXX_COMPILER=clang++-10 -DDYN_OPENAL=OFF",
+            deps_cmdline: "sudo apt update && sudo apt install clang-9 libsdl2-dev libvpx-dev libopenal-dev libfluidsynth-dev libmpg123-dev libsndfile1-dev",
             build_type: "Debug"
           }
         - {