Disable unneeded alsa dependency in ffmpeg

.github/workflows/linux.yml

@@ -221,6 +221,7 @@ jobs:
           --disable-autodetect \
           --disable-everything \
           --disable-neon \
+          --disable-alsa \
           --disable-iconv \
           --enable-libopus \
           --enable-vaapi \

docs/building-cmake.md

@@ -91,6 +91,7 @@ Go to ***BuildPath*** and run
     --disable-autodetect \
     --disable-everything \
     --disable-neon \
+    --disable-alsa \
     --disable-iconv \
     --enable-libopus \
     --enable-vaapi \

snap/snapcraft.yaml

@@ -226,7 +226,6 @@ parts:
     source-branch: release/4.2
     plugin: autotools
     build-packages:
-      - libasound2-dev
       - libopus-dev
       - libva-dev
       - libvdpau-dev
@@ -240,6 +239,7 @@ parts:
       - --disable-autodetect
       - --disable-everything
       - --disable-neon
+      - --disable-alsa
       - --disable-iconv
       - --enable-shared
       - --enable-libdav1d