OpenMP warning on Clang systems

[jbeich]

Regressed by https://github.com/llvm/llvm-project/commit/76b45e874d47. Affects both C and Rust versions. CC @aklv (downstream)

$ pngquant test.png
OMP: Info #276: omp_set_nested routine deprecated, please use omp_set_max_active_levels instead.
$ echo $?
0
$ ls -l foo*.png
-rw-r--r--  1 foo  foo   9920 Jan 13 20:05 test-fs8.png
-rw-r--r--  1 foo  foo  21629 Jan 13 20:02 test.png

$ cc --version
FreeBSD clang version 15.0.6 (https://github.com/llvm/llvm-project.git llvmorg-15.0.6-0-g088f33605d8a)
Target: x86_64-unknown-freebsd14.0
Thread model: posix
InstalledDir: /usr/bin

[kornelski]

Thanks. I've dropped it in 911dce31a8dfbedb0c7c50ccaf49c8e42c20a201