Bug 1321403 - make build work with python3 again, r=mt

Test Plan: .

Reviewers: mt

Reviewed By: mt

Differential Revision: https://nss-review.dev.mozaws.net/D419

--HG--
extra : rebase_source : 7a6bf32bb35934f061ef864d7c0fc214eaad7222

coreconf/werror.py

@@ -24,7 +24,7 @@ def can_enable():
         # If we aren't clang, make sure we have gcc 4.8 at least
         if not cc_is_clang:
             try:
-                v = subprocess.check_output([cc, '-dumpversion'], stderr=sink)
+                v = subprocess.check_output([cc, '-dumpversion'], stderr=sink).decode("utf-8")
                 v = v.strip(' \r\n').split('.')
                 v = list(map(int, v))
                 if v[0] < 4 or (v[0] == 4 and v[1] < 8):