For native package one recomended begin recompile

In your /etc/makepkg.conf

#recomendations
CFLAGS="-march=native -O2 -pipe"
CXXFLAGS="-march=native -O2 -pipe"

So for local repo

Assuming your *.pkg.* is in /src/native-repo

in your /etc/pacman.conf

comment:

[core]
Include = /etc/pacman.d/mirrorlist

[extra]
Include = /etc/pacman.d/mirrorlist

and uncomment:

[custom]
SigLevel = Optional TrustAll
Server = file:///src/native-repo

So next add "trust" or "there are my binaries" for add to pacman

add-repo /src/native-repo/custom.db.tar.gz add-repo -n /src/native-repo/custom.db.tar.gz /src/native-repo/*.pkg.* pacman -Syu