fix(nix-ninja): module-scope genIncsOut -- stop generated -I dirs shadowing standard headers (#79) master
The first genIncsOut appended the $out-relative -I dir of EVERY generated header in the graph to every compile (478 -I flags on a migcom compile in the libSystem graph). That polluted the include search path: libsyscall/mach/string.h shadowed <string.h> for migcom, whose transitive <_types.h> then failed. Scope it to the compiles OWN source module (moduleKey: src/external/<m>) like the per-edge migHeaderIncsFor -- asl.c still gets its sibling aslcommon (same module src/external/syslog) for <asl_ipc.h>, but migcom no longer sees libsyscall dirs. Covers mig + non-mig generated headers via a fresh per-module map. Signed-off-by: Niclas Overby <niclas@overby.me>