Fix build-docs-l10n.sh: resolve coreutils dir to absolute path

The script uses cd then references the dir again, so a relative
path like 'coreutils' breaks. Resolve to absolute at startup.

Author: sylvestre

scripts/build-docs-l10n.sh

@@ -12,7 +12,7 @@
 
 set -euo pipefail
 
-COREUTILS_DIR="${1:?Usage: $0 <coreutils-dir>}"
+COREUTILS_DIR="$(cd "${1:?Usage: $0 <coreutils-dir>}" && pwd)"
 
 # ftl filename -> URL lang code (when they differ)
 declare -A FTL_TO_URL=(