[Toybox] [landley/toybox] weak symbols hack broke the build (Issue #554)

[Rob Landley]

> clang: error: unknown argument '-static-libasan'; did you mean '-static-libsan'?
>
> you should just be able to delete that though, since that was your _previous_ workaround for gcc asan issues.

If you remove "--static-libasan" from the reproduction sequence in 
commit 635f1e0391b0 then on my devuan daedalus (bookworm minus systemd) 
laptop it fails to run with "ASan runtime does not come first in initial 
library list; you should either link runtime to your application or 
manually preload it with LD_PRELOAD."

The first argument on the gcc command line is "-fsanitize=address" and 
gcc itself figured out when to suck in libc and libasan.

The first thing in ldd a.out is linux-vdso.so.1, the second is 
libgtk3-nocsd.so.0 which I did not ask for and this isn't a gui program, 
the third is libasan.so.8 and the fourth is libc.so.6. Then dl, pthread 
(again did not ask), libm, libgcc_s, and ld-linux-x86-64.so.2.

The only library I listed on the command line was the -as-needed 
libcrypt, which got optimized out by libasan (but works fine without 
asan enabled). All the rest of that the distro's gcc sucked in itself, 
in an order I do not control.

At one point you said you were going to poke the llvm guys about 
accepting --static-libasan as an alias for --static-libsan but this is 
an older version of ubuntu than that discussion:

http://lists.landley.net/pipermail/toybox-landley.net/2024-July/030444.html

I can try to teach portability.sh to check the compiler type when 
setting up llvm and use the appropriate variant. A bit brittle for 
comfort, but as it's an optional part of the build...