feat(@angular-devkit/build-angular): provide partial custom postcss c… #8127

Job	Run time
build	2m 20s
lint	2m 2s
e2e_windows (windows-2025, 22, npm, 4)	2m 8s
e2e_windows (windows-2025, 22, npm, 1)	2m 12s
e2e_windows (windows-2025, 22, npm, 2)	2m 11s
e2e_windows (windows-2025, 22, npm, 5)	2m 9s
e2e_windows (windows-2025, 22, npm, 0)	2m 7s
e2e_windows (windows-2025, 22, esbuild, 0)	2m 9s
e2e_windows (windows-2025, 22, npm, 3)	2m 9s
e2e_windows (windows-2025, 22, esbuild, 1)	2m 8s
e2e_windows (windows-2025, 22, esbuild, 2)	1m 59s
e2e_windows (windows-2025, 22, esbuild, 4)	2m 9s
e2e_windows (windows-2025, 22, esbuild, 5)	2m 9s
e2e_windows (windows-2025, 22, esbuild, 3)	2m 9s
publish-snapshots	1s
Browser Compatibility Tests	1s
test	1s
e2e-snapshots	1s
e2e	1s
e2e-package-managers	1s
	30m 7s

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