Fix symlinks to use correct names (externals, generated)

The symlinks were created as externals-link and generated-link, but
the build and cache steps use ./externals and ./generated. Rename so
the secondary disk is actually used.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: jonathanpeppers

.github/workflows/copilot-setup-steps.yml

@@ -27,8 +27,8 @@ jobs:
         
         # Create symlinks to use the secondary disk
         ln -s /mnt/build-output ./output
-        ln -s /mnt/externals ./externals-link
-        ln -s /mnt/generated ./generated-link
+        ln -s /mnt/externals ./externals
+        ln -s /mnt/generated ./generated
         
         echo "Build directories configured:"
         ls -la | grep -E "(output|externals|generated)"