scripts: cros_sdk: check reclient settings

Display an error if only one of these are used since things only work
if both are specified.

BUG=b:191307774
TEST=`cros_sdk` still works

Change-Id: I3b24fbae8f2a0b075907a9590d2dac25e3d5d164
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/4225323
Reviewed-by: Jack Rosenthal <jrosenth@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
diff --git a/scripts/cros_sdk.py b/scripts/cros_sdk.py
index 6a66380..88e5208 100644
--- a/scripts/cros_sdk.py
+++ b/scripts/cros_sdk.py
@@ -1135,6 +1135,13 @@
 
     options.Freeze()
 
+    if options.reclient_dir and not options.reproxy_cfg_file:
+        cros_build_lib.Die("--reclient-dir requires --reproxy-cfg-file")
+    if not options.reclient_dir and options.reproxy_cfg_file:
+        cros_build_lib.Die(
+            "--reproxy-cfg-file only makes sense with --reclient-dir"
+        )
+
     remoteexec = (
         remoteexec_util.Remoteexec(
             options.reclient_dir, options.reproxy_cfg_file