ci: bump dragonflybsd-vm from v1.1.4 to v1.3.4

The DragonFlyBSD lane reports success without ever building. Measured in two
independent runs:

Run 36739123551 (failed overall, 18:25:20 -> 18:47:32, complete log):
  the guest-side shell was Killed twice (SIGKILL, OOM on the runner while a
  nested QEMU runs), and immediately after each kill the action still emitted
  ##[end-action ... outcome=success;conclusion=success]. No build ran in any
  of the three attempts: "meson" 0 occurrences, "running xserver build" 0.
  That is why attempts 1 and 2 were recorded as green.

Run 36763250919 (reported success, 19:11:48 -> 19:15:29, complete log):
  the build script started and meson setup completed ("Build targets in
  project"), then nothing: "Compiling C" 0, "Linking" 0, "meson install" 0.
  Conclusion: success.

So the lane swallows the exit code of the inner command. v1.1.4 is also twelve
tag releases behind; the newest is v1.3.4.

Not a host-load problem, which is why no load metric would have found it: in
run 36762972575 netbsd, freebsd, hurd, gentoo and the image job all succeeded
while dragonflybsd failed, on the same runner class at the same time.

Fixing this restores an actual signal rather than making a broken one louder.
Whether v1.3.4 also fixes the swallowed exit code is to be measured, not
assumed - that is what the CI run on this PR is for.

The other VM lanes are already current: freebsd floats on @v1 and is the most
reliable lane, netbsd was bumped to v1.5.0 when it broke the same way.

Signed-off-by: Enterprise <info@metux.net>

.github/workflows/build-xserver.yml

@@ -639,7 +639,7 @@ jobs:
             - name: run in DragonFlyBSD VM (attempt 1)
               id: dfly-1
               continue-on-error: true
-              uses: vmactions/dragonflybsd-vm@v1.1.4
+              uses: vmactions/dragonflybsd-vm@v1.3.4
               with:
                   envs: 'MESON_ARGS'
                   usesh: true
@@ -656,7 +656,7 @@ jobs:
               id: dfly-2
               if: steps.dfly-1.outcome == 'failure'
               continue-on-error: true
-              uses: vmactions/dragonflybsd-vm@v1.1.4
+              uses: vmactions/dragonflybsd-vm@v1.3.4
               with:
                   envs: 'MESON_ARGS'
                   usesh: true
@@ -671,7 +671,7 @@ jobs:
 
             - name: run in DragonFlyBSD VM (attempt 3)
               if: steps.dfly-1.outcome == 'failure' && steps.dfly-2.outcome == 'failure'
-              uses: vmactions/dragonflybsd-vm@v1.1.4
+              uses: vmactions/dragonflybsd-vm@v1.3.4
               with:
                   envs: 'MESON_ARGS'
                   usesh: true