CI: arm build fix

The commit bd91d16 (2024-05-31) causes the live555 being build on all
platforms, including arm Linux. But the plaform is not valid for that,
so replace linux-64bit with linux.

Also enforce live555 in this case.

.github/scripts/Linux/arm/build.sh

@@ -19,6 +19,7 @@ set -- "$@" --enable-caca --enable-gl-display --enable-panogl_disp --enable-sdl
 set -- "$@" --enable-libavcodec --enable-rtdxt --enable-libswscale --enable-uyvy                        # compression
 set -- "$@" --enable-blank --enable-holepunch --enable-natpmp --enable-pcp --enable-resize --enable-scale --enable-sdp-http --enable-testcard-extras --enable-text --enable-video-mixer --enable-zfec # extras (pp. etc)
 set -- "$@" --enable-drm
+set -- "$@" --enable-rtsp-server
 if [ "$ARCH" = arm64 ]; then
         set -- "$@" --enable-vulkan
 fi

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

@@ -82,7 +82,7 @@ download_build_live555() {
                 # ensure binutils ld is used (not lld)
                 pacman -Sy --noconfirm binutils
         elif [ "$(uname -s)" = Linux ]; then
-                target=linux-64bit
+                target=linux
         else
                 target=macosx
         fi