macOS arm64 build breaks when system lp_solve headers or stale qd artifacts exist

Environment

• macOS Apple Silicon (arm64), Homebrew R 4.5, prefix /opt/homebrew

Problem

R CMD INSTALL . can fail in sequence on Apple Silicon:

1. lp_solve header shadowing: /opt/homebrew/include/lp_types.h is found before the vendored headers, so LPSREAL is missing (e.g., in lp_MDO.c).
2. x86 intrinsics on ARM: external/PackedCSparse/FloatArray.h pulls in <immintrin.h> on ARM, which breaks compilation.
3. wrong-arch qd archive: an old external/PackedCSparse/qd/libqd.a (e.g., built under x86_64/Rosetta) can be reused and cause link architecture mismatches.

Expected

R CMD INSTALL . should succeed on arm64 even if a system lp_solve is installed and/or the tree was previously built under another architecture.

Repro

R CMD INSTALL .