[llvm] [llvm-strings] Use small buffer instead of reading whole file (PR #163073)

[via llvm-commits]

aokblast wrote:

It is even faster than FreeBSD's strings implementation:

blast at blast-devserv ~/G/l/build (strings/fix_oom)> time cat /tmp/test.file | LD_LIBRARY_PATH=../build-crt/lib ./bin/llvm-strings > /dev/null

________________________________________________________
Executed in    4.68 secs    fish           external
   usr time    4.58 secs    1.66 millis    4.58 secs
   sys time    0.35 secs    0.25 millis    0.35 secs

blast at blast-devserv ~/G/l/build (strings/fix_oom)> time cat /tmp/test.file |  strings > /dev/null

________________________________________________________
Executed in    7.82 secs    fish           external
   usr time    7.70 secs    1.98 millis    7.69 secs
   sys time    0.38 secs    0.30 millis    0.38 secs

https://github.com/llvm/llvm-project/pull/163073