Zstdmt count wrong number of cores

[sergey-dryabzhinsky]

On my i7-6850K zstdmt claims there is only 6 cores available. But cpuinfo shows 12 cores, and siblings, command grep -c processor /proc/cpuinfo also shows 12.

To Reproduce Steps to reproduce the behavior:

1. Install zstd v1.5.7; `apt install zstd
2. Run `zsrdmt with flags -14 -v
3. Scroll up on the log to 'Note: 6 physical core(s) detected'
4. See error

Expected behavior Number must be equal to number of siblings or logical coree.

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Desktop (please complete the following information):

• OS: Debian 7+
• Version:1.5.7
• Compiler: gcc 4.7.2
• Flags: -O2
• Other relevant hardware specs: 6-core
• Build system: Debian default