- Create local/docs/PACKAGE-BUILD-QUIRKS.md: central reference for all
known cross-compilation build issues (DYNAMIC_INIT behavior, m4
CFLAGS/LDFLAGS ordering, ninja-build BUILD_TESTING, general patterns)
- Update UPSTREAM-SYNC-PROCEDURE.md: add m4 LDFLAGS ordering quirk
(must be set AFTER DYNAMIC_INIT), ninja-build BUILD_TESTING=OFF,
DYNAMIC_INIT overwrite behavior, source reversion root cause summary
- Update AGENTS.md: reference PACKAGE-BUILD-QUIRKS.md in WHERE TO LOOK
table, add DYNAMIC_INIT and cross-compilation test conventions
- Fix ninja-build recipe: add cmakeflags=['-DBUILD_TESTING=OFF']
(tests require host gtest which conflicts with Redox sysroot stdlib.h)