Xnnpack still builds with `+dotprod` and `+fp16` with `-DXNNPACK_ENABLE_ARM_DOTPROD=OFF -DXNNPACK_ENABLE_ARM_FP16_SCALAR=OFF -DXNNPACK_ENABLE_ARM_FP16_VECTOR=OFF`

I'm building aan Arm64 target with a fairly old toolchain (gcc 7.5, binutils 2.29.1) in order to support old Linux platforms.
I use:
`-DXNNPACK_ENABLE_ARM_BF16=OFF -DXNNPACK_ENABLE_ARM_I8MM=OFF -DXNNPACK_ENABLE_ARM_DOTPROD=OFF -DXNNPACK_ENABLE_ARM_FP16_SCALAR=OFF -DXNNPACK_ENABLE_ARM_FP16_VECTOR=OFF
`
Yet Xnnpack still seems to build with `+dotprod` and `+fp16`:
```
In file included from /home/personau/LinuxToolchainsTest/tflite_aarch64_release/xnnpack/src/f16-dwconv2d-chw/gen/5x5s2p2-minmax-neonfp16arith-1x4.c:12:0:
/home/personau/x-tools/aarch64-unknown-linux-gnu-glibc2.25-gcc7.5/lib/gcc/aarch64-unknown-linux-gnu/7.5.0/include/arm_neon.h:17259:1: note: expected 'const float16_t * {aka const __fp16 *}' but argument is of type 'const uint16_t * {aka const short unsigned int *
'
vld1_dup_f16 (const float16_t* __a)
^~~~~~~~~~~~
cc1: error: invalid feature modifier in '-march=armv8.2-a+fp16+dotprod'
gmake[2]: *** [_deps/xnnpack-build/CMakeFiles/XNNPACK.dir/build.make:4093: _deps/xnnpack-build/CMakeFiles/XNNPACK.dir/src/f16-gemm/gen-inc/1x8inc-minmax-aarch64-neonfp16arith-ld64.S.o] Error 1
gmake[2]: *** Waiting for unfinished jobs....
gmake[1]: *** [CMakeFiles/Makefile2:6137: _deps/xnnpack-build/CMakeFiles/XNNPACK.dir/all] Error 2
gmake[1]: *** Waiting for unfinished jobs....
gmake: *** [Makefile:136: all] Error 2

```