systemd-nspawn seems to be failing under ubsan

[evverx]

Since bf428ef was merged, systemd-nspawn has been failing under ubsan:

$ sudo UBSAN_OPTIONS=print_stacktrace=1 ./build/systemd-nspawn  --register=no -D $CONTAINER_ROOT --setenv=ASAN_OPTIONS=log_path=/asan.log:strict_string_checks=1:detect_stack_use_after_return=1:check_initialization_order=1:strict_init_order=1  -b
...
../src/nspawn/nspawn.c:3994:64: runtime error: left shift of 2097152 by 10 places cannot be represented in type 'int'
    #0 0x56375daa59b6 in initialize_rlimits ../src/nspawn/nspawn.c:3994
    #1 0x56375daa681b in main ../src/nspawn/nspawn.c:4056
    #2 0x7f1a6e4dcf29 in __libc_start_main (/lib64/libc.so.6+0x20f29)
    #3 0x56375da458b9 in _start (/home/vagrant/systemd/build/systemd-nspawn+0x8b8b9)
...

I haven't looked at the code carefully yet, so I'm not sure whether it's a false positive or not.