Details on this package are located in Section 10.5.2, “Contents of Linux-Headers.”
The Linux Headers package contains the “sanitized” kernel headers.
Install the header files that are needed for the base build:
install -dv /tools/include
cp -av include/{asm-generic,asm-i386,asm-x86_64,linux} /tools/include/
cp -av include/asm-x86_64-biarch /tools/include/asm
Details on this package are located in Section 10.5.2, “Contents of Linux-Headers.”