fix(@angular/build): resolve style include paths relative to `ng-pack… #2814

Job	Run time
build	26s
lint	2m 2s
build-e2e-windows	29s
publish-snapshots	0s
Browser Compatibility Tests	0s
test	0s
e2e-package-managers	0s
e2e-snapshots	0s
e2e	0s
e2e-windows	0s
	2m 57s

Provide feedback