drm: measure the verification deb glibc floor and put it in the artifact name

The workflow already said in a comment that this deb is a verification build
with a higher glibc floor than the release debs, because it builds on the
runner rather than in the ubuntu18.04 container the stock job uses. A comment
in this file is not visible to whoever downloads the artifact from the Actions
UI, and the name was a bare rustdesk-unattended-wayland-x86_64.deb, so it read
like something installable anywhere.

The floor is now read off the built object with objdump and goes into the
artifact name, so the constraint travels with the file. Measured rather than
stated: a hardcoded number would drift the next time the runner image moves.
Verified the pipeline against a real deb here (2.39).

Restoring the container build is the other option and is cheap to do -- the
recipe including the two 18.04 traps is still in this repo's history -- but it
belongs with a deb that is actually distributed, not with a job whose contents
are already asserted in-place.

.github/workflows/drm-capture.yml

@@ -298,11 +298,27 @@ jobs:
           dpkg -c "$deb" | grep -E 'usr/lib/rustdesk/libdrmtap\.so\.0 ->'
           mv "$deb" "${deb%.deb}-x86_64.deb"
 
-      # Verification artifact, deliberately NOT a release deliverable: it is built on the runner rather
-      # than in the old container the stock release debs use, so its glibc floor is higher. The consent
-      # free variant stays out of the published release either way.
+      # MEASURE the glibc floor rather than describing it. This job builds on the runner instead of the
+      # ubuntu18.04 container the stock release debs use, so the artifact only runs on a host at least
+      # as new as the runner -- and that number belongs in the artifact NAME, because a comment in this
+      # file is not visible to whoever downloads it from the Actions UI.
+      - name: Measure the deb glibc floor
+        id: floor
+        shell: bash
+        run: |
+          deb="$(ls rustdesk-unattended-wayland-*-x86_64.deb)"
+          rm -rf /tmp/debfloor && dpkg-deb -R "$deb" /tmp/debfloor
+          floor="$(objdump -T /tmp/debfloor/usr/share/rustdesk/lib/librustdesk.so \
+                   | grep -oE 'GLIBC_2\.[0-9]+' | sort -uV | tail -1)"
+          test -n "$floor"
+          echo "floor=${floor#GLIBC_}" >> "$GITHUB_OUTPUT"
+          echo "::notice::deb requires ${floor} or newer (built on the runner, not the ubuntu18.04 release container)"
+
+      # Verification artifact, deliberately NOT a release deliverable. The consent-free variant stays
+      # out of the published release either way; the name states the floor so nobody installs it on an
+      # older distro and hits a bare loader error.
       - name: Upload the deb
         uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
         with:
-          name: rustdesk-unattended-wayland-x86_64.deb
+          name: rustdesk-unattended-wayland-x86_64-verification-glibc${{ steps.floor.outputs.floor }}.deb
           path: rustdesk-unattended-wayland-*-x86_64.deb