* Only use ENOSR and ENOPKG if defined
ENOSR and ENOPKG are part of the POSIX optional STREAMS extension, and
are not available on most other platforms than GNU/Linux.
* Support building on other GNU platforms than Linux
Build for other GNU platforms the same way as Linux: this includes
CMAKE_SYSTEM_NAME "GNU" (GNU/Hurd) and "GNU/kFreeBSD" (GNU/kFreeBSD).
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