unittests: Do not use syscall library: does not work well with cimport

test/unit/helpers.lua

@@ -96,8 +96,6 @@ cimportstr = function(body)
       print(lnum, line)
     end
   end
-  body = body:gsub('//.*', '')
-  body = body:gsub('/%*.*%*/', '')
   body = formatc(body)
   body = filter_complex_blocks(body)
 
@@ -139,10 +137,6 @@ cimportstr = function(body)
   return libnvim
 end
 
-ffi.cdef = cimportstr
-local syscall = require('syscall')
-ffi.cdef = cdef
-
 local function cppimport(path)
   return cimport(Paths.test_include_path .. '/' .. path)
 end