Export `CMAKE_PREFIX_PATH` in helper installation scripts #24355

Job	Run time
Build and test (linux-gnu-real32-32)	18m 9s
Build and test (linux-gnu-real64-32)	18m 27s
Build and test (linux-gnu-complex64-32)	17m 21s
Build and test (linux-gnu-complex128-32)	20m 33s
Build and test (linux-gnu-real64-64)	26m 10s
Build and test (linux-gnu-complex128-64)	19m 59s
	2h 0m 39s

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