class-version.sh: work around new hexdump bug

It seems that newer versions of hexdump do not allow seeking from stdin
anymore? At least, that's what others online have concluded:

    https://www.medo64.com/2021/06/hexdumps-illegal-seek/

Fortunately, in this case, we can just decode all 8 of the first bytes,
and then take the last 4.

Author: ctrueden

Diff for: ci-setup-github-actions.sh

@@ -5,7 +5,8 @@
 #
 
 echo "BUILD_REPOSITORY=https://github.com/${GITHUB_REPOSITORY}"
-echo "BUILD_OS=${RUNNER_OS}" 
+echo "BUILD_OS=${RUNNER_OS}"
+echo "BUILD_DEPLOY_FORBIDDEN=..." # CTR START HERE - use GITHUB-specific env vars set upon PR to decide this
 
 echo "BUILD_REPOSITORY=https://github.com/${GITHUB_REPOSITORY}" >> $GITHUB_ENV
 echo "BUILD_OS=${RUNNER_OS}" >> $GITHUB_ENV

Diff for: class-version.sh

@@ -4,7 +4,7 @@
 
 class_version() {
   # extract bytes 4-7
-  info=$(head -c 8 | hexdump -s 4 -e '4/1 "%d\n" "\n"')
+  info=$(head -c 8 | hexdump -e '4/1 "%d\n" "\n"' | tail -n4)
   minor1="$(echo "$info" | sed -n 1p)"
   minor2="$(echo "$info" | sed -n 2p)"
   major1="$(echo "$info" | sed -n 3p)"