scripts: Run crossdev with --stable

This allows us to force --ex-pkg entries to use their stable versions instead of using the latest.

BUG=b:276349781
TEST=sudo cros_setup_toolchains \
     -t armv7a-cros-linux-gnueabihf \
     --nousepkg

Change-Id: I0ab3081a98f3c8ab7851f12c408d38275cbda0d8
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/4408128
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Jordan Abrahams-Whitehead <ajordanr@google.com>
Tested-by: Jordan Abrahams-Whitehead <ajordanr@google.com>
Reviewed-by: Manoj Gupta <manojgupta@chromium.org>
Reviewed-by: George Burgess <gbiv@chromium.org>
diff --git a/scripts/cros_setup_toolchains.py b/scripts/cros_setup_toolchains.py
index 228a1cc..eedf978 100644
--- a/scripts/cros_setup_toolchains.py
+++ b/scripts/cros_setup_toolchains.py
@@ -220,7 +220,7 @@
                 )
             else:
                 # Build the crossdev command.
-                cmd = ["crossdev", "--show-target-cfg", "--ex-gdb"]
+                cmd = ["crossdev", "--stable", "--show-target-cfg", "--ex-gdb"]
                 # Enable libxcrypt for all linux-gnu targets.
                 if "cros-linux-gnu" in target:
                     cmd.extend(CROSSDEV_LIBXCRYPT_ARGS)
@@ -292,7 +292,7 @@
             config_only: Just update.
         """
         configured_targets = cls._CACHE.setdefault("configured_targets", [])
-        cmdbase = ["crossdev", "--show-fail-log"]
+        cmdbase = ["crossdev", "--stable", "--show-fail-log"]
         cmdbase.extend(["--env", "FEATURES=splitdebug"])
         # Pick stable by default, and override as necessary.
         cmdbase.extend(["-P", "--oneshot"])