pkg.sh: log-install: Don't log by default

cmd_log_install() defaults $c_logfile to "install.log", so every
invocation without -l appends to an install.log in the current
directory. That's semantical nonsense.

Default $c_logfile to empty instead. The existing empty-$c_logfile
early exit already skips logging, so no -l now means no log, and
callers that want a log pass -l explicitly, as the packaging flow
does through INSTALL_LOG.

Assisted-by: unsloth/Qwen3.8-27B-GGUF:Q4_K_M (pi)
Signed-off-by: Jan Lindemann <jan@janware.com>

scripts/pkg.sh

@@ -734,7 +734,7 @@ cmd_log_install()
 	local args="$*"
 
 	local c_format=rpm
-	local c_logfile=install.log
+	local c_logfile=""
 	local c_mode_dir=false
 	local c_create_leading_dirs=false
 	local c_group=`id -gn`