cmake: dts: Use temporary file for dts.cmake #146422

Job	Run time
twister-build-prep	2m 59s
twister-build (1)	28m 29s
twister-build (2)	31m 29s
twister-build (3)	30m 20s
twister-build (4)	32m 36s
twister-build (5)	19m 47s
twister-build (6)	28m 6s
twister-build (7)	24m 55s
Publish Unit Tests Results	13s
Check Twister Status / all jobs passed	2s
	3h 18m 56s

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