chore: CI build times optimization (DDC caching)

[tustanivsky]

This PR reduces Unreal sample app build time by caching Derived Data Cache between CI runs.

The DDC stores precompiled shaders generated during the project’s content cooking. Since building these shaders takes most of the time and the results remain unchanged unless project assets (such as materials) or graphics settings are modified, there’s no need to rebuild them on every run.

Benchmarks

🐧 Linux

UE Version	on: main	on: ci/build-times	Improvement
UE 4.27	24m 18s	14m 44s	↓ 9m 34s
UE 5.1	1h 1m	14m 41s	↓ 46m 19s
UE 5.2	42m 37s	15m 4s	↓ 27m 33s
UE 5.3	44m 10s	18m 39s	↓ 25m 31s
UE 5.4	54m 29s	14m 49s	↓ 39m 40s
UE 5.5	1h 5m	23m 32s	↓ 41m 28s
UE 5.6	57m 26s	26m 8s	↓ 31m 18s

🪟 Windows

UE Version	on: main	on: ci/build-times	Improvement
UE 4.27	43m 39s	25m 42s	↓ 17m 57s
UE 5.0	1h 13m	34m 12s	↓ 38m 48s
UE 5.1	1h 37m	33m 28s	↓ 1h 3m
UE 5.2	1h 19m	34m 0s	↓ 45m
UE 5.3	1h 15m	31m 35s	↓ 43m 25s
UE 5.4	1h 43m	37m 40s	↓ 1h 6m
UE 5.5	1h 55m	36m 20s	↓ 1h 19m
UE 5.6	2h 3m	40m 48s	↓ 1h 22m

📊 Summary

Platform	Longest job (main)	Longest job (ci/build-times)	Improvement
🐧 Linux	1h 5m	26m	↓ ~60%
🪟 Windows	2h 3m	41m	↓ ~67%

Related to:

• CI Pipeline Improvements for Cross-Platform Support #1002

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