Improve build perf

[joaomoreno]

Several perf problems with the build that need to be addressed:

• All agents do the same compilation/optimization/minification
• Each extension get compiled/optimized/webpacked 6 (!) times
• node.exe gets downloaded 2 times
• macOS agents seem slower than before, though they end up doing more than others:
  • Sourcemaps
  • Bundle stats (Submitted bundle stats)

DONE ✔️

• Remove VSCODE_WEB hack, create vscode-web-* tasks
• De-duplicate compilation tasks
  • Remove old extensions compilation
  • Dedupe extensions build
  • Cleanup Node.JS downloading
  • Dedupe Node.JS downloading
  • Dedupe vscode build
    • Alpine
    • ARM
• Verify Webpack catches TS type errors
• Use the Yarn cache task
• Run common steps only once in a separate Linux build agent
  • Hygiene
  • Compilation
  • Optimization & minification
  • Cache result in VSTS artifacts, such that other agents and successive build resubmissions can simply pick that up
• Have VSCODE_COMPILE_ONLY flag
• Get template for arm/alpine
• Remove node build/lib/builtInExtensions.js
• Move quality/*/package.json dependencies into actual package.json dependencies
• Deduplicate extension compilation Remove legacy extensions compilation from build #77058
• Cleanup VSCODE_ARCH usages in Linux build 7b0cd32
• Set sensible values for task timeout
• Lower agent parallel jobs
• Move sourcemaps to common agent
• Move bundle stats to common agent
• Move upload-configuration to common agent

---

Task	Step	Windows	Linux	macOS	Unit
Prepare build		11	6.5	7.5	min
Build		25	21	45	min
VS Code	compile-client-build	170	160	215	sec
	optimize-vscode	31	31	86	sec
	minify-vscode	152	139	290	sec
	vscode-win32-x64-min	259	191	436	sec
Server	compile-client-build	146	134	198	sec
	optimize-vscode-reh	5	5	16	sec
	minify-vscode-reh	27	23	79	sec
	vscode-reh-win32-x64-min	169	113	312	sec
Web	compile-client-build	148	136	188	sec
	optimize-vscode-reh	27	28	64	sec
	minify-vscode-reh (web)	134	120	273	sec
	vscode-reh-win32-x64-min (web)	167	116	329	sec
Unit		1.5	1	1.5	min
Integration		9	0	8	min
Publish		6	4	0.5	min

[joaomoreno]

Removing old extensions build and deduping extension webpacking across all three targets brought the build time down from 1114s to 379s: 3x speedup.

[joaomoreno]

Deduping TypeScript compilation brought it further down to 264s: 4x speedup.

[joaomoreno]

Merged deduplication effort. Here are the improvements for the build step, given two sample builds:

Step	Before	After	Speedup
Windows	23m	15m	1.5x
Windows32	27m	15m	1.8x
Linux	19m	10m	1.9x
LinuxArmHf	6m	6m	1x
LinuxAlpine	14m	8m	1.75x
macOS	41m	16m	2.5x

[joaomoreno]

Adding Yarn cache:

Step	Before	After	Speedup
Windows (x64, ia32)	9m	4m	2.3x
Linux (x64, arm, alpine)	4m	2m	2x
macOS	4m	3m	1.3x

[joaomoreno]

Here are some really exciting numbers for the shared agent which runs hygiene checks, telemetry gathering and core & extensions compilation:

Type of Build	Duration
No Cache	15m
Cached Dependencies (99% of builds)	10m
Rebuild Same Commit	3m

Platform specific agents can just pick up this agent's work and proceed with testing, packaging, signing and publishing.

[joaomoreno]

Some more preliminary numbers, for total build times:

Step	Before	After	Speedup
Windows	58m	44m	1.3x
Windows32	59m	46m	1.3x
Linux	38m	23m	1.7x
LinuxArmHf	22m	21m	1x
LinuxAlpine	23m	26m	0.9x
macOS	68m	42m	1.6x

There's still a bit more to go through. We're still compiling extensions twice unnecessarily, for example.