chore: replace make with $(MAKE) in example Makefile

[Integral-Tech]

Description

• Replace make with $(MAKE) in example Makefile

Motivation and Context

According to GNU Make Manual,

Recursive make commands should always use the variable MAKE, not the explicit command name make.

How Has This Been Tested?

Screenshots / Output (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (no code change)
• Refactor (refactoring production code)
• Other

Checklist:

• My code follows the code style of this project.
• I have updated the documentation and changelog accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.
• Rustfmt and Rust-clippy passed.