improve ifort rootdir

Author: waruqi

xmake/modules/detect/sdks/find_ifortenv.lua

@@ -53,7 +53,11 @@ function _load_ifortvars(ifortvars_bat, arch, opt)
     file:close()
 
     -- run genifortvars.bat
-    os.run(genifortvars_bat)
+    local oneapi_rootdir = os.getenv("ONEAPI_ROOT")
+    if not oneapi_rootdir then
+        oneapi_rootdir = path.directory(ifortvars_bat)
+    end
+    os.runv(genifortvars_bat, {envs = {ONEAPI_ROOT = oneapi_rootdir}})
 
     -- load all envirnoment variables
     local variables = {}