build: [gyp] cdm key system support behind flag

[deepak1556]

Description of Change

Align with https://github.com/electron/electron/pull/14423 for the gyp build.

Checklist

• [x] PR description included and stakeholders cc'd
• [x] Patch information is added to appropriate .patches.yaml
• [x] script/update runs without error
• [x] PR title follows semantic commit guidelines

[alexeykuzmin]

Something is not ok with the ARM build configs/scripts.

[deepak1556]

@alexeykuzmin have fixed them, thanks!

[alexeykuzmin]

@ckerr 👍