cmake: mcuboot: Do not make a RAM load slot 1 bin file #237916

Job	Run time
twister-build-prep	3m 51s
twister-build (2)	24m 53s
twister-build (4)	30m 22s
twister-build (5)	30m 19s
twister-build (7)	18m 54s
twister-build (1)	38m 35s
twister-build (8)	26m 1s
twister-build (3)	25m 9s
twister-build (6)	15m 20s
Publish Unit Tests Results	1m 30s
Check Twister Status / all jobs passed	2s
	3h 34m 56s

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