D260 - Per-file objects, so a build recompiles only what changed

status: measured

Every C target compiled all of its sources in a single clang <every .c> -o target command. So every build recompiled everything - surface.c and its thirty-five-thousand-symbol census included - make could not skip an unchanged file, -j had nothing to parallelise inside one compile, and a compiler cache could not cache a multi-file compile-and-link at all.

Each target now compiles each source to its own .o and links the objects. Measured:

	before (monolithic)	after
edit one file, rebuild module	full recompile (~30-60 s)	1.5 s
clean module rebuild, cache warm	~30-60 s	2.6 s
script rebuild, nothing changed	tens of seconds	7 s

The object-built eboot was run on hardware and behaves identically - same report, same tally, GEN unknown, clean display - so the link from objects is equivalent to the monolithic compile-and-link.

The correctness hazard, and how it is handled. make decides what to rebuild from file times, not from compile flags. This project flips GEN, DISPLAY_MEM, EXCLUDE and more between builds, and reusing an object built with the old value would be a silently wrong binary

• which costs a hardware cycle to notice, the worst kind of wrong here. Each object depends on a per-target .flags sentinel that is rewritten, and so made newer than every object, exactly when the flag string changes; a flag change therefore forces a full recompile. Verified: touch one file → one object rebuilds; change DISPLAY_MEM → all eighty-eight rebuild.

The flags are written to the sentinel with make's $(file ...) function rather than through the shell, because they carry embedded quotes - -DOBSCENE_BUILD_ID='"dev"' - that no shell quoting survives. $(file) evaluates when make expands the recipe, before any mkdir in that recipe would run, so the object directories are made by an order-only prerequisite instead.

Link-only flags (-nostdlib, the -Wl, group) are kept off the compile line and -D/-I/ warning flags off the link line: each is an unused argument in the other phase, and -Werror turns an unused-argument warning into a failure.

CC stays :=, not ?=: ?= loses to make's built-in cc default, which would quietly build with gcc. A command-line make CC="sccache clang" overrides := and is how the cache wraps in.

The payload target is left monolithic - it is off the package path and rarely built, so the restructure is scoped to host, module and eboot.