ctx: use -O2 not -O3

Benchmarks from using debug overlay:

O3 settings menu: 13-15fps system menu 18fps sun menu 17-18fps O2 settings menu: 16-17fps system menu 23fps sun menu 20fps

added 3 commits

• 90bf0a46 - 1 commit from branch main
• ff8379c6 - README: typofix
• 5bda6917 - ctx: use -O2 not -O3

Compare with previous version

additional datapoints, sorted by descending speed for the color fills in menus/nick.

Os: settings: 19fps system: 26fps sun: 21fps clouds: 7-8fps nick: 35-37fps

Oz: settings: 18fps system: 24fps sun: 21fps clouds: 7-8fps nick: 35-37fps

O2: settings: 16-17fps system: 23fps sun: 20fps clouds: 8-9fps nick: 33-34fps

Ofast: settings: 14fps system: 19fps sun: 17fps clouds: 10-11fps nick: 31-32fps

O3: settings: 13-15fps system: 18fps sun: 17-18fps clouds: 9-10fps nick: 30-32fps

approved this merge request

merged