Fix up regression execution to better handle tests that end abnormally.

E.g., mark aborts due to assertion failures as failed tests,
but those that get killed by the user as needing to be rerun, etc.

src/python/m5/config.py

@@ -29,10 +29,18 @@
 import os
 from os.path import isdir, isfile, join as joinpath
 
-homedir = os.environ['HOME']
-confdir = os.environ.get('M5_CONFIG', joinpath(homedir, '.m5'))
+
+confdir = os.environ.get('M5_CONFIG')
+
+if not confdir:
+    # HOME is not set when running regressions, due to use of scons
+    # Execute() function.
+    homedir = os.environ.get('HOME')
+    if homedir and isdir(joinpath(homedir, '.m5')):
+        confdir = joinpath(homedir, '.m5')
+
 def get(name):
-    if not isdir(confdir):
+    if not confdir:
         return None
     conffile = joinpath(confdir, name)
     if not isfile(conffile):