debian/control: Add libxsimd-dev build dependency for vendored Arrow

debian/control: Add libxsimd-dev build dependency for vendored Arrow

In commit e8460cbd, we introduced the "pkg.ceph.arrow" build profile to
support building with system Arrow packages. However, neither Debian nor
Ubuntu currently ships Arrow packages.

Since WITH_RADOSGW_SELECT_PARQUET is always enabled in debian/rules,
Arrow support is required for all builds. When the pkg.ceph.arrow profile
is not selected, the build uses vendored Arrow, which requires building
xsimd as one of its third-party dependencies. Without libxsimd-dev
available, builds fail in cleanroom environments that lack network access.

This commit adds libxsimd-dev as a build dependency when pkg.ceph.arrow
is not selected, satisfying the vendored Arrow build requirements and
enabling successful builds in network-restricted environments.

Signed-off-by: Kefu Chai <k.chai@proxmox.com>