sandbox: Disable Ctrl-C

This is not supported properly on sandbox, and interferes with running
tests, since when a test script is piped in, some commands will call
ctrlc() which will drop characters from the test script.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/common/console.c b/common/console.c
index 898da39..5a2f411 100644
--- a/common/console.c
+++ b/common/console.c
@@ -524,6 +524,7 @@
 static int ctrlc_was_pressed = 0;
 int ctrlc(void)
 {
+#ifndef CONFIG_SANDBOX
 	if (!ctrlc_disabled && gd->have_console) {
 		if (tstc()) {
 			switch (getc()) {
@@ -535,6 +536,8 @@
 			}
 		}
 	}
+#endif
+
 	return 0;
 }
 /* Reads user's confirmation.