test(e2e): don't let wait on the killed holder abort 171 (exit 143)

`wait` on a job we just killed returns 143, and it sat as the last command of an
`&&` list under `set -e` — so on Windows the script died the moment the mapping
was released, before asserting anything about the build it had just run. Probed
the shell semantics directly rather than guessing: the old form exits 143 on
Linux too, it only never ran there because HOLDER is empty on POSIX.

Author: Sunrisepeak

tests/e2e/171_bmi_staging_locked_dest.sh

@@ -89,7 +89,10 @@ set +e
 "$MCPP" build -v > build2.log 2>&1
 rc=$?
 set -e
-[[ -n "$HOLDER" ]] && { kill "$HOLDER" 2>/dev/null; wait "$HOLDER" 2>/dev/null; }
+# `wait` on a job we just killed returns 143, and under `set -e` that would
+# abort the script right here — with the build's own result never asserted.
+# (Exactly how this test failed on Windows the first time it got that far.)
+[[ -n "$HOLDER" ]] && { kill "$HOLDER" 2>/dev/null || true; wait "$HOLDER" 2>/dev/null || true; }
 chmod 644 "$DST" 2>/dev/null || true
 
 if [[ $rc -ne 0 ]]; then