CH32V003 fails to boot with non-empty BSS

[burgrp]

As soon as there is something in BSS section i.e. it has non-zero size, CH32V003 hangs on boot. It is caused by wrong calculation of address in the assembly code:

            \\    li a0, 0
            \\    la a1, microzig_bss_start
            \\    la a2, microzig_bss_end
            \\    beq a1, a2, clear_bss_done
            \\clear_bss_loop:
            \\    sw a0, 0(a1)
            \\    addi a1, a1, 4
            \\    blt a1, a2, clear_bss_loop
            \\clear_bss_done:

replacing la a1, microzig_bss_start with lui a1, 0x20000 "fixes" the issue.

Proper fix seems to be to link image with flash section starting at 0x instead of 0x8000000.

[burgrp]

Fixed in PR 618.