[9fans] risc-v port progress at IWP9

[Ron Minnich <rminnich@p9f.org>]

Daniel and Shawn made good progress on the risc-v port, and their
experience reminded me of a standard test I used to use while doing
ports.

long story short, for blue gene and other ports (early amd64) we added
this test in main

ulong x = 0x12345678;

main()
{
    if (x != 0x12345678) panic("unaligned data"):

...


how can this test fail? x is in the data segment, but the immediate in
the test is in the text segment. This test is a quick and easy way to
check if your data segment is correctly loaded in memory.

In some ports, the data is aligned by code in l.s that moves it.

There are some really nasty, confusing errors that will arise in a
seemingly working kernel if data is not aligned.

I always add this test when I'm doing a port. It catches a problem
that is otherwise very confusing, and presents as strings  not set up
right, variables wrong, etc.

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