Revert "Add libc6-dev as build dependency"

This reverts commit 27d9fbcb510b56a847f33ad7e10ba6a9ac1824f4.
Revert "Revert "Change back to gcc with memory limit""

This reverts commit 44d17c27beac4819bd2160b741d38fe91959c69e.
Higher memory limit

Signed-off-by: Lance Chen <cyen0312@gmail.com>