Fix 7za.exe invocation on Windows

Author: vahook

utils/buildactions/utils.lua

@@ -96,7 +96,7 @@ function os.sha256_file(path)
 	local windows = os.host() == "windows"
 	local s, errc
 	if windows then
-		s, errc = os.outputof(string.format("utils\\7z\\7za.exe h -scrcSHA256 \"%s\"", path))
+		s, errc = os.outputof(string.format("call \"utils\\7z\\7za.exe\" h -scrcSHA256 \"%s\"", path))
 	else
 		s, errc = os.outputof(string.format("sha256sum \"%s\" | awk '{ print $1 }'", path))
 	end