Support running regtests.py outside .ini directory

Now it is possible to give an absolute or relative path to the .ini
file, rather than needing to invoke regtests.py from the directory in
which the .ini file is located.

suite.py

@@ -402,7 +402,7 @@ def __init__(self, args):
         # and build directories
         self.repos = {}
 
-        self.test_file_path = os.getcwd() + '/' + self.args.input_file[0]
+        self.test_file_path = os.path.abspath(self.args.input_file[0])
 
         self.suiteName = "testDefault"
         self.sub_title = ""