Fixes broken shell prompt in Terminal and adb shell
Before: https://del.dog/7vphlkc
After: https://del.dog/vhkjgo8
Add as prebuilt with suffix "_twrp" to avoid conflict
with original mkshrc and rename via POST_INSTALL_CMD
Prebuilt version adjusts TMPDIR variable from
"/data/local/tmp" to "/tmp" for TWRP
Change-Id: I42a1b2a8c114f66dbe659c07485f1dfae8a5d314
Captain Throwback