The qbz/qbzd source builds set only !lto; makepkg then injects -C
debuginfo=2 for its debug package, which inflates the final rustc link
enough to trip the OOM killer on the qbz-qt binary. Add !debug so the
source packages link within a normal builder's memory. Verified by
clean container builds of qbz and qbzd 2.1.0.
cc