add helper function for get_arch_value

misc/build.func

@@ -3838,6 +3838,7 @@ build_container() {
   export ENABLE_TUN="$ENABLE_TUN"
   export PCT_OSTYPE="$var_os"
   export PCT_OSVERSION="$var_version"
+  export PCT_ARCH="$(dpkg --print-architecture 2>/dev/null || uname -m)"
   export PCT_DISK_SIZE="$DISK_SIZE"
   export IPV6_METHOD="$IPV6_METHOD"
   export ENABLE_GPU="$ENABLE_GPU"

misc/core.func

@@ -360,6 +360,26 @@ arch_check() {
   fi
 }
 
+# ------------------------------------------------------------------------------
+# get_arch_value()
+#
+# - Selects an architecture-specific value while preserving amd64 defaults
+# - Usage: get_arch_value "amd64-value" "arm64-value"
+# - Defaults: amd64="amd64", arm64="arm64"
+# ------------------------------------------------------------------------------
+get_arch_value() {
+  local amd64_val="${1:-amd64}"
+  local arm64_val="${2:-arm64}"
+  case "$PCT_ARCH" in
+  amd64) echo "$amd64_val" ;;
+  arm64) echo "$arm64_val" ;;
+  *)
+    msg_error "Unsupported architecture: $PCT_ARCH"
+    return 106
+    ;;
+  esac
+}
+
 # ------------------------------------------------------------------------------
 # ssh_check()
 #