fix: Use os_uname() to check for Linux

[cryptomilk]

In build environments like Fedora's mockbuild, there is no OSTYPE environment variable set. Use a more secure method to detect Linux. Details:

man os-release https://www.man7.org/linux/man-pages/man5/os-release.5.html

[zhaozg]

I think should use https://github.com/luvit/luv/blob/master/docs.md#uvos_uname

[cryptomilk]

I've changed it.

[cryptomilk]

The minimum supported libuv doesn't provide os_uname(). What now, fall back to /etc/os-release?

[Bilal2453]

I don't think simply checking if /etc/os-release exists is as reliable either! As far as I know, it is a systemd thing that may not exists on non-systemd distribution. The most reliable way I know of for detecting if the OS is Linux based (works on Android environments as well) is by checking uname --kernel-name (uname -s), this will require an io.popen most likely, roughly something like this:

local popen_handle = io.popen('uname -s')
local uname_os = assert(popen_handle:read('*a'))
popen_handle:close()
isLinux = uname_os:lower() == 'linux'

I would also like to point out that in the current code it seems to me like isLinux is set to nil instead of false if the OS is not Windows but also isn't Linux (for example, when the OS is openbsd and jit isn't available).

[cryptomilk]

I've updated it to use uname -s.

/etc/os-release is a freedesktop standard, it also has been added to Python 3.10, see https://docs.python.org/3/library/platform.html#platform.freedesktop_os_release

[cryptomilk]

Looks like popen() is not alway available?

[squeek502]

Looks like popen is dependent on LUA_USE_POSIX being defined, which we currently don't do. Adding

IF(NOT WIN32)
  ADD_DEFINITIONS(-DLUA_USE_POSIX)
ENDIF(NOT WIN32)

to lua.cmake is probably a good idea in general and should fix the error.

[Bilal2453]

@squeek502 I think the CI tests need to be manually re-triggered?

[cryptomilk]

I've tested it with fedora mockbuild and the patch works fine.