chore[test]: use uv.os_uname() to check OS sysname if avail

lib/utils.lua

@@ -12,18 +12,24 @@ else
   usecolors = false
 end
 
-if _G.jit and _G.jit.os then
-  -- Luajit provides explicit platform detection
-  utils.isWindows = _G.jit.os == "Windows"
-  utils.isLinux = _G.jit.os == 'Linux'
+if (uv.os_uname) then
+  local uname = assert(uv.os_uname())
+  utils.isWindows = uname.sysname == "Windows"
+  utils.isLinux = uname.sysname == 'Linux'
 else
-  -- Normal lua will only have \ for path separator on windows.
-  utils.isWindows = package.config:find("\\") and true or false
-  local f = io.popen('uname', 'r')
-  if f then
-    local line = f:read("*l")
-    utils.isLinux = line == 'Linux'
-    f:close()
+  if _G.jit and _G.jit.os then
+    -- Luajit provides explicit platform detection
+    utils.isWindows = _G.jit.os == "Windows"
+    utils.isLinux = _G.jit.os == 'Linux'
+  else
+    -- Normal lua will only have \ for path separator on windows.
+    utils.isWindows = package.config:find("\\") and true or false
+    if not utils.isWindows then
+      local _os = os.getenv('RUNNER_OS') or os.getenv('OSTYPE')
+      if (_os and _os:lower():match('linux')) then
+        utils.isLinux = true
+      end
+    end
   end
 end