kunit: use --build_dir=.kunit as default

To make KUnit easier to use, and to avoid overwriting object and
.config files, the default KUnit build directory is set to .kunit

 * Related bug: https://bugzilla.kernel.org/show_bug.cgi?id=205221

Fixed up minor merge conflicts - Shuah Khan <skhan@linuxfoundation.org>

Signed-off-by: Vitor Massaru Iha <vitor@massaru.org>
Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

tools/testing/kunit/kunit.py

@@ -169,7 +169,7 @@ def add_common_opts(parser):
 	parser.add_argument('--build_dir',
 			    help='As in the make command, it specifies the build '
 			    'directory.',
-			    type=str, default='', metavar='build_dir')
+                            type=str, default='.kunit', metavar='build_dir')
 	parser.add_argument('--make_options',
 			    help='X=Y make option, can be repeated.',
 			    action='append')
@@ -245,12 +245,11 @@ def main(argv, linux=None):
 	cli_args = parser.parse_args(argv)
 
 	if cli_args.subcommand == 'run':
-		if cli_args.build_dir:
-			if not os.path.exists(cli_args.build_dir):
-				os.mkdir(cli_args.build_dir)
-			kunit_kernel.kunitconfig_path = os.path.join(
-				cli_args.build_dir,
-				kunit_kernel.kunitconfig_path)
+                if not os.path.exists(cli_args.build_dir):
+                    os.mkdir(cli_args.build_dir)
+                kunit_kernel.kunitconfig_path = os.path.join(
+                        cli_args.build_dir,
+                        kunit_kernel.kunitconfig_path)
 
 		if not linux:
 			linux = kunit_kernel.LinuxSourceTree()