Description:
`extra/xxhash` package cannot be build with AVX enabled, as a result users with relatively new CPUs are unable to rebuild it with `-march=native`, and this is unfortunate. Thankfully the problem can be solved by appending -mno-avx` to users' CFLAGS by editing PKGBUILD like this:
```
build() {
CFLAGS+=" -mno-avx"
make PREFIX=/usr DISPATCH=1 -C xxHash
}
```

* package version: 0.8.2-1

Steps to reproduce:
1. open `/etc/makepkg.conf` set CFLAGS="-march=x86-64-v3 -O3 -pipe", for example.
2. Download the latest version of `extra/xxhash` package and try to build it with `makepkg`.
3. You will get the following error:
```
xxh_x86dispatch.c:85:4: error: #error "Do not compile xxh_x86dispatch.c with AVX enabled! See the comment above."
```