fix(Makefile): track CUTE scala sources in Makefile

[ecall73]

Summary

• Make now tracks Scala sources in both src/main/scala and CUTE/src/main/scala.
• This ensures CUTE-internal Scala edits trigger rebuild of related RTL outputs.
• Added optional-directory handling to avoid parse-time find noise when CUTE is absent.

Workstream And Scope

• Primary workstream: XSAI RTL flow / build orchestration
• Main paths touched:
  • Makefile
• Coupled areas or upstream links:
  • None; dependency-list update only

Review Focus

• Confirm dependency tracking now covers CUTE/src/main/scala.
• Confirm no side effects for environments where CUTE is not initialized.

[Copilot]

Pull request overview

This PR updates the build dependency tracking in the top-level Makefile so that changes to Scala sources under the optional CUTE/src/main/scala tree will correctly trigger regeneration of RTL outputs, while avoiding find errors when CUTE is not present.

Changes:

• Add a SCALA_DIRS list that includes ./src/main/scala plus ./CUTE/src/main/scala when it exists.
• Update SCALA_FILE discovery to run find over SCALA_DIRS, ensuring CUTE-internal Scala edits participate in rebuild triggering.

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[yu-yake2002]

After we merged multiple new precisions into the master, the compilation speed decreased significantly. Next, it is necessary to optimize the compilation speed. @Wonicon