ci(docs) replace use of sed with proper configuration variables

docs/build.py

@@ -32,14 +32,8 @@ ex.exec()
 
 urlpath = re.sub('release/', '', br)
 
-# Be sure the GitHub links point to the right branch
-f = open("header.rst", "w")
-f.write(".. |github_link_base| replace:: https://github.com/lvgl/lvgl/blob/" + gitcommit + "/docs")
-f.close()
-
-base_html = "html_baseurl = 'https://docs.lvgl.io/" + urlpath + "/en/html/'"
-
-os.system("sed -i \"s|html_baseurl = .*|" + base_html +"|\" conf.py")
+os.environ['LVGL_URLPATH'] = urlpath
+os.environ['LVGL_GITCOMMIT'] = gitcommit
 
 clean = 0
 trans = 0