Device tests updates (#9246)

Stop pyexpect from closing serial port when running with WSL2
Remove makefile flags & opts making it too silent. At some point it makes a lot of useful info just disappear. There are external means of silencing make, so probably best to leave useful data always available

Replace SPIFFS with LittleFS in FS test
Re-use certs-from-mozilla.py in FS test

Fix libc tests w/o -fno-builtin not actually testing anything, also add the flag via .globals.h in case it breaks
Fix libc tests generating warnings when using invalid (but safe) size arguments

libraries/ESP8266WiFi/examples/BearSSL_CertStore/certs-from-mozilla.py

@@ -13,15 +13,9 @@ import os
 import sys
 from shutil import which
 
-from subprocess import Popen, PIPE, call
-try:
-    from urllib.request import urlopen
-except Exception:
-    from urllib2 import urlopen
-try:
-    from StringIO import StringIO
-except Exception:
-    from io import StringIO
+from io import StringIO
+from subprocess import Popen, PIPE, call, CalledProcessError
+from urllib.request import urlopen
 
 # check if ar and openssl are available
 if which('ar') is None and not os.path.isfile('./ar') and not os.path.isfile('./ar.exe'):
@@ -62,10 +56,10 @@ for i in range(0, len(pems)):
     thisPem = pems[i].replace("'", "")
     print(names[i] + " -> " + certName)
     ssl = Popen(['openssl','x509','-inform','PEM','-outform','DER','-out', certName], shell = False, stdin = PIPE)
-    pipe = ssl.stdin
-    pipe.write(thisPem.encode('utf-8'))
-    pipe.close()
-    ssl.wait()
+    ssl.communicate(thisPem.encode('utf-8'))
+    ret = ssl.wait()
+    if ret != 0:
+        raise CalledProcessError(ret, certName)
     if os.path.exists(certName):
         derFiles.append(certName)
         idx = idx + 1