Use native open/io.open for file contents reading/writing

platformio/builder/tools/piolib.py

@@ -82,7 +82,8 @@ class LibBuilderFactory(object):
                     fname, piotool.SRC_BUILD_EXT + piotool.SRC_HEADER_EXT
                 ):
                     continue
-                content = fs.get_file_contents(join(root, fname))
+                with open(join(root, fname)) as fp:
+                    content = fp.read()
                 if not content:
                     continue
                 if "Arduino.h" in content and include_re.search(content):

platformio/builder/tools/piomaxlen.py

@@ -18,7 +18,6 @@ from hashlib import md5
 from os import makedirs
 from os.path import isdir, isfile, join
 
-from platformio import fs
 from platformio.compat import WINDOWS, hashlib_encode_data
 
 # Windows CLI has limit with command length to 8192
@@ -67,7 +66,8 @@ def _file_long_data(env, data):
     )
     if isfile(tmp_file):
         return tmp_file
-    fs.write_file_contents(tmp_file, data)
+    with open(tmp_file, "w") as fp:
+        fp.write(data)
     return tmp_file