Disable terser for server build

[timneutkens]

Checking the stats first. But at least until #6950 is figured out we should disable it for serverless builds as it's also disabled for zeit.co serverless builds.

[github-actions]

Stats from current PR

Click to expand stats

	zeit/next.js canary	timneutkens/next.js add/disable-terser-serverless-bundles	Change
Build Duration	12.6s	13.1s	⚠️ +508ms
node_modules Size	44 MB	44 MB	-731 B
Total Bundle (main, webpack, commons) Size	202 kB	202 kB	✓
Total Bundle (main, webpack, commons) gzip Size	66.3 kB	66.3 kB	✓
Client _app Size	2.49 kB	2.49 kB	✓
Client _app gzip Size	1.04 kB	1.04 kB	✓
Client _error Size	8.85 kB	8.85 kB	✓
Client _error gzip Size	3.31 kB	3.31 kB	✓
Client pages/index Size	298 B	298 B	✓
Client pages/index gzip Size	235 B	235 B	✓
Client pages/link Size	3.28 kB	3.28 kB	✓
Client pages/link gzip Size	1.49 kB	1.49 kB	✓
Client pages/routerDirect Size	426 B	426 B	✓
Client pages/routerDirect gzip Size	304 B	304 B	✓
Client pages/withRouter Size	408 B	408 B	✓
Client pages/withRouter gzip Size	293 B	293 B	✓
Client main Size	24.6 kB	24.6 kB	✓
Client main gzip Size	8.03 kB	8.03 kB	✓
Client commons Size	175 kB	175 kB	✓
Client commons gzip Size	57 kB	57 kB	✓
Client webpack Size	1.49 kB	1.49 kB	✓
Client webpack gzip Size	774 B	774 B	✓
Base Rendered Size	1.34 kB	1.34 kB	✓
Build Dir Size	340 kB	340 kB	✓

Click to expand serverless stats

	zeit/next.js canary	timneutkens/next.js add/disable-terser-serverless-bundles	Change
Build Duration	17.1s	14.1s	-3s
node_modules Size	44 MB	44 MB	-731 B
Total Bundle (main, webpack, commons) Size	202 kB	202 kB	✓
Total Bundle (main, webpack, commons) gzip Size	66.3 kB	66.3 kB	✓
Client _app Size	2.49 kB	2.49 kB	✓
Client _app gzip Size	1.04 kB	1.04 kB	✓
Client _error Size	8.85 kB	8.85 kB	✓
Client _error gzip Size	3.31 kB	3.31 kB	✓
Client pages/index Size	298 B	298 B	✓
Client pages/index gzip Size	235 B	235 B	✓
Client pages/link Size	3.28 kB	3.28 kB	✓
Client pages/link gzip Size	1.49 kB	1.49 kB	✓
Client pages/routerDirect Size	426 B	426 B	✓
Client pages/routerDirect gzip Size	304 B	304 B	✓
Client pages/withRouter Size	408 B	408 B	✓
Client pages/withRouter gzip Size	293 B	293 B	✓
Client main Size	24.6 kB	24.6 kB	✓
Client main gzip Size	8.03 kB	8.03 kB	✓
Client commons Size	175 kB	175 kB	✓
Client commons gzip Size	57 kB	57 kB	✓
Client webpack Size	1.49 kB	1.49 kB	✓
Client webpack gzip Size	774 B	774 B	✓
Serverless pages/link Size	223 kB	307 kB	⚠️ +83.7 kB
Serverless pages/link gzip Size	58.8 kB	79.1 kB	⚠️ +20.3 kB
Serverless pages/index Size	218 kB	300 kB	⚠️ +81.2 kB
Serverless pages/index gzip Size	57.6 kB	77.2 kB	⚠️ +19.6 kB
Serverless pages/_error Size	220 kB	300 kB	⚠️ +80.6 kB
Serverless pages/_error gzip Size	57.5 kB	77 kB	⚠️ +19.4 kB
Serverless pages/routerDirect Size	219 kB	300 kB	⚠️ +81.4 kB
Serverless pages/routerDirect gzip Size	57.6 kB	77.3 kB	⚠️ +19.7 kB
Serverless pages/withRouter Size	219 kB	300 kB	⚠️ +81.4 kB
Serverless pages/withRouter gzip Size	57.6 kB	77.4 kB	⚠️ +19.8 kB
Build Dir Size	1.32 MB	1.73 MB	⚠️ +408 kB