Add build info

Also remove "-fpie" because this won't work with it enabled, most likely
because "-fpie" creates some .got* sections that probably should be
loaded into "RAM" (0x00231000) at some point, but that never happens
since those sections aren't in the linker script. As it is now, even
with the option enabled, the code was never truly position-independent
due to the fixed "RAM" address, so once I fix that issue (by letting RAM
start immediately after ROM), have a separate .rodata section without
the executable bit set (for cleaner disassembly), and properly load the
.got* sections, I can re-enable that option.