Bug#790571: please give-back capnproto on mipsel

Hi,
I have tested capnproto on a few local machines.
Initially, build failed on all boards.
On different MIPS boards, different tests were failing.


AsyncUnixTest.WriteObserver fails if the kernel PAGESIZE is larger that 4k.

After I reduced PAGESIZE to 4096 on CI20, all tests passed.

The solution could be to increase buffer size:
> char buffer[4096] 
(src/kj/async-unix-test.c++ +416)
I had increased it to 16384 and tried it on Loongson 3A
(PAGESIZE is 16k, same board as mipsel-manda-01, mipsel-manda-02),
all test passed.
We should keep on mind that pagesize on some MIPS board is up to 64k.
This solution should be discussed upstream.


On EdgeRouter Pro (mips-aql-02),
these two test failed:
> [  FAILED  ] 2 tests, listed below:
> [  FAILED  ] AsyncUnixTest.SignalWithValue
> [  FAILED  ] AsyncUnixTest.SignalWithPointerValue

I will do further investigating.

Best Regards,
Dejan