Update the sanity limit from 200M to 220M per file.

[SuperHacker-liuan]

This is needed because the librustc_driver-*.so filesize on some targets
now exceed 200M. i.e. nightly-mips64el-unknown-linux-gnuabi64

This will close #2362.

The commit e23a7be , in which we lift the limit
from 100M to 200M, was commited 9 monthes ago. Thus we can estimate that the
driver size will grow 10M per month on nightly-mips64el target. With extra 20M
limit, we will be able to perform a better solution in about 2 monthes.

Signed-off-by: LIU An [email protected]

[rbtcollins]

I'd like to keep this as low as possible: this defines the minimum acceptable memory budget and we already run into out of memory issues on smaller devices: I don't think that the driver size is going to double in the near term : so I'd suggest 220M or something like that. We're obviously going to have to work on permitting chunking with threaded IO for the future, but right now, machines with less available unpack ram will trigger a panic -

if max_file_size > unpack_ram {
            panic!("RUSTUP_UNPACK_RAM must be larger than {}", max_file_size);
        }

[SuperHacker-liuan]

How about set the limit to 250M.

The commit which update the limit from 100M to 200M, was merged 9 monthes ago ( commit e23a7be ), which means the driver size will grow 10M per month in average.

If we set the liimit to 220M, we will have 2 monthes to solve this problem, if set to 250M, we will have about half year to solve this.

[SuperHacker-liuan]

@rbtcollins Well, I repushed a patch, and set the limit to 220M. Hope we can perform a better solution before the limit exceed again😀