Create my own advanced Makefile

[ericsandu]

Add Makefile for compiling greetings.c and twoparter built from part1.c, part2.c and header.h

The makefile uses the wildcard function, variables for file states and compiler flags and multiple declaration formats for build rules

All operations and their behaviours are explained in comments inside the file

[Copilot]

Pull request overview

Adds a custom GNU Make Makefile intended to build two small C executables (greeting and twoparter) and provide a clean target, as part of the repository’s gnumake/ examples.

Changes:

• Introduces gnumake/custom/Makefile with all, greeting, twoparter, and clean targets.
• Adds variables for compiler selection and flags, and attempts to use wildcard to detect built executables.

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[Copilot]

ifdef GREETING_EXISTS / ifdef TWOPARTER_EXISTS will always evaluate true here because both variables are assigned unconditionally (and are non-empty). This makes clean try to remove files even when they don’t exist, and rm will fail the target. Prefer rm -f greeting twoparter, or use ifneq ($(wildcard greeting),) style checks instead of ifdef.

[ericsandu]

Fixed by assigning NULL value instead of 0 in variables

[Copilot]

PR description mentions compiling greetings.c, but the Makefile (and the directory contents) refer to greeting.c. Please align the PR description with the actual filename (or rename the target/source if the intention was greetings.c).