Install busybox on the x86 Android emulator

install_busybox.sh

#!/bin/bash
wget "http://www.busybox.net/downloads/binaries/latest/busybox-i486" -O /tmp/busybox
adb push /tmp/busybox /data/data/busybox
adb shell "mount -o remount,rw /system && mv /data/data/busybox /system/bin/busybox && chmod 755 /system/bin/busybox && /system/bin/busybox --install /system/bin"

The current busybox installer is inside .../busybox/ so I made a few modifications to make it work.

#!/bin/bash
wget --no-parent --no-host-directories --cut-dirs 3 -r https://busybox.net/downloads/binaries/1.30.0-i686/ -P /tmp/busybox
adb push /tmp/busybox /data/data/busybox
adb shell "mount -o rw,remount /system && mv /data/data/busybox /system/bin/busybox && chmod 755 /system/bin/busybox/busybox && /system/bin/busybox/busybox --install /system/bin"

with the current Android emulator, you have to start the emulator with "-writable-system" in order to remount and make modifications to the system folder. e.g.:
emulator -avd "Pixel_2_XL_API_27" -writable-system

The current busybox installer is inside .../busybox/ so I made a few modifications to make it work.

#!/bin/bash
wget --no-parent --no-host-directories --cut-dirs 3 -r https://busybox.net/downloads/binaries/1.30.0-i686/ -P /tmp/busybox
adb push /tmp/busybox /data/data/busybox
adb shell "mount -o rw,remount /system && mv /data/data/busybox /system/bin/busybox && chmod 755 /system/bin/busybox/busybox && /system/bin/busybox/busybox --install /system/bin"

Could it be that you have an error in the path of the last command?
As far as I see it (and successfully tried it) it should be:

adb shell "mount -o rw,remount /system && mv /data/data/busybox /system/bin/busybox && chmod 755 /system/bin/busybox && /system/bin/busybox --install /system/bin"

I could not remount /system on an API 30 emulator. disable-verity left me with a non-bootable emulator. Instead of trying to fix it I tried using an API 25 emulator, without running into that issue.

If you need to run on a later API level, perhaps https://android.stackexchange.com/questions/186630/android-o-failed-to-mount-system-dev-block-dm-0-is-read-only helps.