[Toybox] [PATCH] xargs: fix for 32-bit.

[enh]

This affects both arm and x86, causing a signed comparison rather than
an unsigned one.

Here's arm:

      if (data <= (char *)2) data = 0;
   51ecc:       2902            cmp     r1, #2
   51ece:       d905            bls.n   51edc <xargs_main+0x158>

      if ((long)data <= 2) data = 0;
   51ecc:       2902            cmp     r1, #2
   51ece:       dc02            bgt.n   51ed6 <xargs_main+0x152>

And x86 was similiar (and was where I first stumbled across this bug):

      if (data <= (char *)2) data = 0;
   73ad7:       83 f8 02                cmp    $0x2,%eax
   73ada:       76 12                   jbe    73aee <xargs_main+0x223>

      if ((long)data <= 2) data = 0;
   73ad7:       83 f8 02                cmp    $0x2,%eax
   73ada:       7e 12                   jle    73aee <xargs_main+0x223>

For some reason, on the desktop I seem to see heap addresses low enough
to not appear negative, whereas Android seems to fail every time.
jemalloc is presumably more likely to allocate high?

While I'm here, make it clearer that we're ignoring the allocated length
argument to getdelim(), and stop storing the actual length at all
because we don't use it afterwards. This wasn't _wrong_, but it was a
red herring when I started debugging.
---
 toys/posix/xargs.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)
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