fix(Makefile): add libkrun.dylib symlink for EFI builds on macOS

[flavioaiello]

Fix macOS EFI build: add libkrun.dylib symlink for pkg-config compatibility

Problem

When building libkrun on macOS with EFI=1, the library is installed as libkrun-efi.1.dylib, but libkrun.pc references -lkrun. This causes linking failures for consumers using pkg-config:

ld: library 'krun' not found

Affected consumers include krun-sys (the Rust FFI bindings in this repo) and any other project using pkg-config --libs libkrun.

Solution

Add a libkrun.dylib symlink pointing to libkrun-efi.1.dylib during installation when building with EFI on Darwin. This aligns the installed library with what libkrun.pc declares.

Changes

In the install: target, after the EFI library is installed:

ifeq ($(OS),Darwin)
ifeq ($(EFI),1)
	cd $(DESTDIR)$(PREFIX)/$(LIBDIR_$(OS))/ ; ln -sf libkrun-efi.$(ABI_VERSION).dylib libkrun.dylib
endif
endif

Why this approach?

• Minimal change - Single symlink, no changes to .pc.in or krun-sys
• Consistent with Linux - Linux uses libkrun.so; macOS now has matching libkrun.dylib
• Standard practice - Unix library versioning commonly uses symlinks
• Intent-preserving - The .pc file already uses libkrun as the stable API name

Testing

After this fix:

# Build and install with EFI
make EFI=1
sudo make EFI=1 install

# Verify symlink exists
ls -la /usr/local/lib/libkrun.dylib
# libkrun.dylib -> libkrun-efi.1.dylib

# pkg-config now works
pkg-config --libs libkrun
# -L/usr/local/lib -lkrun

# krun-sys builds without manual workarounds
cd krun-sys && cargo build