worflow: fixes to os case switch in shader build script

scripts/compile_sokol_shaders.sh

@@ -1,5 +1,7 @@
 #!/bin/bash
 
+OS=$(uname -s)
+
 path_root="$(git rev-parse --show-toplevel)"
 path_backend="$path_root/backend"
 path_scripts="$path_root/scripts"
@@ -13,6 +15,11 @@ case "$OS" in
     Linux*)
         sokol_shdc="$path_sokol_tools/bin/linux/sokol-shdc"
         ;;
+    *)
+        echo "Unsupported operating system: $OS"
+        CoreCount_Physical=1
+        CoreCount_Logical=1
+        ;;
 esac
 echo "Using sokol-shdc: $sokol_shdc"
 chmod +x "$sokol_shdc"