M9.R.37.2: fix launcher $@ clobber that silently dropped --automated args

ROOT CAUSE OF THE M9.R.36 SILENT WEDGE.

reproos-installer-launcher.sh used set -- "$d"/*.so* inside a
loop body to check whether a /nix/store/*/lib dir had any *.so* files
before adding it to LD_LIBRARY_PATH.  set -- overwrites the
script's positional parameters ($@) on every iteration.  The launcher
later did exec env ... /usr/bin/reproos-installer "$@" — but by
then $@ had been clobbered to whatever the LAST loop iteration's glob
expanded to.  By alphabetical /nix/store ordering that was
/nix/store/.../pcsclite-2.3.0-lib/lib/*.so*, so the installer was
exec-ed with six libpcsclite .so paths as its argv — and --automated
/etc/reproos/auto-config.toml was silently DROPPED.

Consequence: the installer fell into GUI mode (no --automated flag),
constructed a QQmlApplicationEngine, loaded main.qml, walked every
nix-store /lib dir in LD_LIBRARY_PATH searching for libc.so.6 +
QtQuick.Controls.  That dlopen() churn (visible in
/tmp/installer.strace as an unending sequence of ENOENT openat calls
against /nix/store/*/lib/libc.so.6) looked like a silent wedge but
was just slow non-progress.  The actual install() function never
ran, which is why Phase 1 / Phase 2 / appendLog stderr lines never
appeared.

FIX: wrap the glob-existence test in a subshell so $@ is not
clobbered:

    if ( set -- "$d"/*.so*; [ -e "$1" ] ); then ... fi

The same buggy pattern lived in the sister GUI launcher
(/usr/bin/reproos-installer-launcher); that one execs sway not the
installer so the user-visible symptom was masked, but the fix is
identical and lands here too as a regression guard.

Diagnostic infrastructure from M9.R.37.1 (strace -f -ttt + kernel
stack sampler + stdbuf -oL -eL) stays in place — useful for future
gaps.  The current sampler tracks PID $$ recorded BEFORE the strace
exec; after exec $$ becomes strace itself (which sits in do_wait),
so the visible kernel stacks are strace's wait4, not the installer's.
Re-run with this fix should expose Phase 1+'s actual behaviour.

Author: zah

recipes/reproos-iso/scripts/stage-de-rootfs.sh

@@ -474,13 +474,20 @@ fi
 # Debian-installed libc.so.6 with a foreign nix-store glibc (which
 # would break every Debian binary in the chain).
 _repro_nix_dirs=""
+# M9.R.37.2 — use a subshell for the glob-existence test so the
+# script's positional parameters ($@) are not clobbered.  This GUI
+# launcher doesn't pass $@ to the installer (it execs sway, then sway
+# execs the installer via SWAY_INIT), but the hygiene fix matches the
+# sister-launcher fix in the ``.sh`` variant and prevents future
+# regressions.
 for d in /nix/store/*/lib; do
   [ -d "$d" ] || continue
   case "$d" in
     /nix/store/*-glibc-*/lib) continue ;;
   esac
-  set -- "$d"/*.so*
-  [ -e "$1" ] || continue
+  if ! ( set -- "$d"/*.so*; [ -e "$1" ] ); then
+    continue
+  fi
   if [ -z "$_repro_nix_dirs" ]; then
     _repro_nix_dirs="$d"
   else
@@ -603,15 +610,26 @@ _repro_nix_libs=""
 _repro_qt_plugins=""
 _repro_qml_imports=""
 _repro_qpa_plugins=""
+# M9.R.37.2 — DO NOT use ``set -- "$d"/*.so*`` to test for the glob
+# existence: ``set --`` overwrites the script's positional parameters
+# ($@), which is what we ultimately pass to ``reproos-installer``.
+# The previous M9.R.36.1 launcher (this script's prior shape) clobbered
+# $@ on every loop iteration and ended up exec-ing the installer with
+# the LAST nix-store dir's ``*.so*`` glob expansion as its argv —
+# silently dropping ``--automated /etc/reproos/auto-config.toml``,
+# so the installer fell into GUI mode + QML engine init + endless
+# dlopen() churn through LD_LIBRARY_PATH (the M9.R.36 "silent wedge
+# after Qt init").  Use a subshell's exit code instead: if the first
+# entry of the expansion exists, the subshell succeeds; otherwise it
+# fails.  $@ is untouched.
 for d in /nix/store/*/lib; do
   [ -d "$d" ] || continue
   # Skip glibc dirs — Debian system glibc must remain canonical so
   # every Debian binary in the live ISO chain keeps working.
   case "$d" in
     /nix/store/*-glibc-*/lib) continue ;;
   esac
-  set -- "$d"/*.so*
-  if [ -e "$1" ]; then
+  if ( set -- "$d"/*.so*; [ -e "$1" ] ); then
     if [ -z "$_repro_nix_libs" ]; then
       _repro_nix_libs="$d"
     else