Alpine Linux How to install x86 packages on x86_64 architecture

Actually, only one file defines which packages take from alpine repos. It is /etc/apk/arch:

# cat /etc/apk/arch 
x86_64

Its value shows which packages we should take from our alpine repos:

# cat /etc/apk/repositories 
http://dl-cdn.alpinelinux.org/alpine/v3.7/main
http://dl-cdn.alpinelinux.org/alpine/v3.7/community

So, we can make a trick here. We can "switch" alpine to get x86 packages from the repos:

/ # echo "x86" > /etc/apk/arch
/ # apk add --no-cache libcurl
fetch http://dl-cdn.alpinelinux.org/alpine/v3.7/main/x86/APKINDEX.tar.gz
fetch http://dl-cdn.alpinelinux.org/alpine/v3.7/community/x86/APKINDEX.tar.gz
(1/12) Replacing musl (1.1.18-r2 -> 1.1.18-r2)
(2/12) Replacing busybox (1.27.2-r8 -> 1.27.2-r8)
Executing busybox-1.27.2-r8.post-upgrade
(3/12) Replacing alpine-baselayout (3.0.5-r2 -> 3.0.5-r2)
Executing alpine-baselayout-3.0.5-r2.pre-upgrade
Executing alpine-baselayout-3.0.5-r2.post-upgrade
(4/12) Replacing libressl2.6-libcrypto (2.6.3-r0 -> 2.6.3-r0)
(5/12) Replacing libressl2.6-libssl (2.6.3-r0 -> 2.6.3-r0)
(6/12) Replacing zlib (1.2.11-r1 -> 1.2.11-r1)
(7/12) Replacing apk-tools (2.8.2-r0 -> 2.8.2-r0)
(8/12) Replacing scanelf (1.2.2-r1 -> 1.2.2-r1)
(9/12) Replacing musl-utils (1.1.18-r2 -> 1.1.18-r2)
(10/12) Installing ca-certificates (20171114-r0)
(11/12) Installing libssh2 (1.8.0-r2)
(12/12) Installing libcurl (7.57.0-r0)
Executing busybox-1.27.2-r8.trigger
Executing ca-certificates-20171114-r0.trigger
OK: 5 MiB in 14 packages