meson: Restrict block subsystem processing

Avoid generating module_block.h and block-gen.c if we are
not going to use them.

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210122204441.2145197-6-philmd@redhat.com>
[Extend to nearby files and directories. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
1 file changed