Fix COLUMNSTORE in Debian CI builds

Debian building tried to implicitly enable ColumnStore, but for this
to work, the boost/flex dependencies need to be there.

Also add `arm64` to the supported platforms for ColumnStore, that is
what it is identified as in Debian 11.

debian/control

@@ -7,7 +7,7 @@ Build-Depends: bison,
                cracklib-runtime <!nocheck>,
                debhelper (>= 10),
                dh-exec,
-               flex [amd64],
+               flex [amd64 arm64],
                gdb <!nocheck>,
                libaio-dev [linux-any],
                libboost-atomic-dev [amd64 arm64],