scripts: Remove original name and timestamp from compressed man pages

This makes man pages in apt packages reproducible. The gzip options were copied from
https://salsa.debian.org/dpkg-team/dpkg/-/blob/1.22.6/scripts/Dpkg/Compression.pm?ref_type=tags#L65

scripts/build/termux_step_massage.sh

@@ -104,7 +104,7 @@ termux_step_massage() {
 		find ./${ADDING_PREFIX}share/man -mindepth 1 -maxdepth 1 -type d ! -name man\* | xargs -r rm -rf
 
 		# Compress man pages with gzip:
-		find ./${ADDING_PREFIX}share/man -type f ! -iname \*.gz -print0 | xargs -r -0 gzip
+		find ./${ADDING_PREFIX}share/man -type f ! -iname \*.gz -print0 | xargs -r -0 gzip -9 -n
 
 		# Update man page symlinks, e.g. unzstd.1 -> zstd.1:
 		while IFS= read -r -d '' file; do