ci: fix arch build

Dockerfile.arch

@@ -1,9 +1,11 @@
-FROM archlinux
+FROM archlinux:latest
 
 ENV TERM=xterm
 ENV CC="ccache gcc"
 
-RUN pacman -Syu --noconfirm
+RUN pacman-key --refresh-keys
+RUN pacman -Syyu --noconfirm
+
 # reflector is optional - if it fails due to network issues, continue with default mirrorlist
 RUN pacman -S --needed --noconfirm reflector && \
     (reflector --latest 20 --protocol https --sort rate --save /etc/pacman.d/mirrorlist || true)