feat: add compositor capability

programs/GNUmakefile

@@ -404,11 +404,19 @@ $(BINDIR)/os/wallpapers/%: $(WPDIR)/%
 	cp $< $@
 
 # Build each system program from its source files.
-$(BINDIR)/os/%.elf: src/%/main.cpp link.ld GNUmakefile $(LIBC_LIB)
+# -MMD records the headers main.cpp pulled in, so editing a shared header
+# (montauk/capabilities.h, Api/Syscall.hpp, ...) rebuilds every program that
+# uses it. A missing depfile matches the empty rule below, which forces a
+# rebuild; that is how programs built before this tracking existed catch up.
+$(BINDIR)/os/%.elf: src/%/main.cpp link.ld GNUmakefile $(LIBC_LIB) obj/%/main.elf.d
 	mkdir -p $(BINDIR)/os obj/$*
-	$(CXX) $(CXXFLAGS) -c src/$*/main.cpp -o obj/$*/main.o
+	$(CXX) $(CXXFLAGS) -MMD -MP -MT $@ -MF obj/$*/main.elf.d -c src/$*/main.cpp -o obj/$*/main.o
 	$(CXX) $(CXXFLAGS) $(LDFLAGS) obj/$*/main.o $(LIBC_LIB) -o $@
 
+obj/%/main.elf.d: ;
+.PRECIOUS: obj/%/main.elf.d
+-include $(wildcard obj/*/main.elf.d)
+
 # ============================================================================
 # Native development kit (Montauk SDK): binutils built for MontaukOS
 # plus a target sysroot (headers, libc.a, crt objects) under 0:/sdk.