Support building Core Lightning as a static library for C/C++ integration

[erickcestari]

It would be valuable for Core Lightning (CLN) to officially support building as a static library (.a) that can be easily linked into external C or C++ projects. This would simplify and standardize integration of CLN functionality into other codebases.

Current Workaround

While working on integrating Core Lightning into bitcoinfuzz, I implemented a workaround by appending the following rule to the end of the Makefile:

libcln.a: libccan.a $(BITCOIN_OBJS) $(COMMON_OBJS) $(WIRE_OBJS) $(EXTERNAL_LIBS) $(CCAN_OBJS)
	@$(call VERBOSE, "ar $@", $(AR) r $@ $(BITCOIN_OBJS) $(COMMON_OBJS) $(WIRE_OBJS) $(CCAN_OBJS))
	@echo "Extracting external libraries..."
	@for lib in ${EXTERNAL_LIBS}; do \
    echo "Processing $$lib"; \
    if [ -f "$$lib" ]; then \
        tmpdir=$$(mktemp -d); \
        echo "Created temp dir: $$tmpdir"; \
        fullpath="$$(pwd)/$$lib"; \
        echo "Full path: $$fullpath"; \
        (cd $$tmpdir && $(AR) x "$$fullpath" && echo "Extraction completed successfully"); \
        if [ -n "$$(ls -A $$tmpdir)" ]; then \
            echo "Found object files: $$(ls $$tmpdir)"; \
            $(AR) r $@ $$tmpdir/*.o; \
        else \
            echo "Warning: No object files found in $$lib"; \
        fi; \
        rm -rf $$tmpdir; \
    else \
        echo "Warning: Library $$lib not found"; \
    fi; \
done

Request

I believe that officially supporting static library builds would benefit many integration projects beyond bitcoinfuzz. This would provide a more maintainable and supported approach to linking CLN components into other projects.

Potential Benefits

• Simplified integration with external C/C++ projects
• Reduced setup complexity for projects needing CLN functionality
• Better compatibility with various build systems
• Improved developer experience when incorporating CLN