CI Linux: simplify caches

handle cache build/install (transitively) in prepare.sh

.github/scripts/Linux/install_ffmpeg.sh

@@ -124,4 +124,9 @@ install_cached() {
         sudo ldconfig
 }
 
-"${1?action required!}"
+deps
+if [ -d $cache_dir ]; then
+        install_cached
+else
+        build_install
+fi

.github/scripts/Linux/install_others.sh

@@ -66,6 +66,7 @@ install_rav1e() {(
 
 # FFmpeg master needs at least v1.3.277 as for 6th Mar '25
 install_vulkan() {(
+        sudo apt build-dep libvulkan1
         git clone --depth 1 https://github.com/KhronosGroup/Vulkan-Headers
         mkdir Vulkan-Headers/build
         cd Vulkan-Headers/build

.github/scripts/Linux/install_sdl.sh

@@ -46,4 +46,9 @@ install_cached() {
         sudo cmake --install fluidsynth/build
 }
 
-"${1?action required!}"
+deps
+if [ -d $cache_dir ]; then
+        install_cached
+else
+        build_install
+fi

.github/scripts/Linux/prepare.sh

@@ -35,9 +35,6 @@ sudo apt install libopencv-core-dev libopencv-imgproc-dev
 sudo apt install libcurl4-openssl-dev # for RTSP client (vidcap)
 sudo apt install i965-va-driver-shaders libva-dev # instead of i965-va-driver
 
-"$dir/install_sdl.sh" deps
-"$dir/install_ffmpeg.sh" deps
-
 sudo apt install qt6-base-dev qt6-wayland
 . /etc/os-release # source ID and VERSION_ID
 if [ "$ID" = ubuntu ] && [ "$VERSION_ID" = 22.04 ]; then
@@ -53,3 +50,6 @@ qt6.conf" "/usr/lib/$(uname -m)-linux-gnu/qt-default/qtchooser/default.conf"
 
 "$GITHUB_WORKSPACE/.github/scripts/Linux/install_others.sh"
 
+"$dir"/install_sdl.sh
+"$dir"/install_ffmpeg.sh
+

.github/scripts/install-common-deps.sh

@@ -49,6 +49,9 @@ download_build_aja() {
 }
 
 install_aja() {(
+        if [ "$(uname -s)" = Linux ]; then
+                sudo apt install libudev-dev
+        fi
         if [ ! -d libajantv2 ]; then
                 download_build_aja
         fi