databases/mongodb50: Disable LTO by default.

Building mongo with LTO enabled takes a ridiculously amount of memory
(32GB in amd64).
Disable -ggdb so memory requirements don't sky rocket (around 10-12GB)

PR: 264340
Reported by: ulassayginim@gmail.com
Approved by: ronald-lists@klop.ws (maintainer)

(cherry picked from commit 0aabc02be18794a56c436233e59379ebaa86c2e0)