Add CMake build support for IBM Z #6043

Job	Run time
msys2 (CLANG64, int32, Release)	17m 39s
msys2 (UCRT64, int32, Release)	13m 55s
msys2 (UCRT64, int64, Release)	13m 23s
neoverse_build	7m 58s
msys2 (MINGW32, int32, Release)	16m 55s
msys2 (CLANG64, int64, Release)	15m 26s
cross_build (mips64el, mips64el-linux-gnuabi64, DYNAMIC_ARCH=1 TARGET=GENERIC)	3m 55s
build (ubuntu-latest, gfortran, cmake)	46m 37s
msys2 (UCRT64, int32, None, mingw-w64-ucrt-x86_64, fc)	13m 12s
cross_build (alpha, alpha-linux-gnu, TARGET=EV4)	2m 40s
cross_build (mipsel, mipsel-linux-gnu, TARGET=MIPS1004K)	4m 0s
build (macos-latest, gfortran, make)	6m 5s
cross_build (riscv64, riscv64-linux-gnu, TARGET=RISCV64_GENERIC)	2m 50s
build (macos-latest, gfortran, cmake)	41m 0s
build (ubuntu-latest, flang, cmake)	10m 42s
build (ubuntu-latest, flang, make)	4m 51s
build (ubuntu-latest, gfortran, make)	21m 19s
	4h 2m 27s

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