Add cross-compilation parameters for RISCV64 targets in CMake #5928

Job	Run time
build (ubuntu-latest, flang, cmake)	45m 22s
build (ubuntu-latest, gfortran, cmake)	46m 1s
neoverse_build	7m 33s
build (macos-latest, gfortran, make)	11m 10s
msys2 (UCRT64, int32, Release)	1h 40m 14s
msys2 (UCRT64, int64, Release)	1h 40m 53s
build (ubuntu-latest, gfortran, make)	22m 45s
build (ubuntu-latest, flang, make)	17m 51s
msys2 (MINGW32, int32, Release)	1h 6m 18s
build (macos-latest, gfortran, cmake)	35m 4s
msys2 (CLANG64, int64, Release)	1h 9m 8s
msys2 (CLANG64, int32, Release)	1h 10m 44s
cross_build (mips64el, mips64el-linux-gnuabi64, DYNAMIC_ARCH=1 TARGET=GENERIC)	9m 43s
cross_build (mipsel, mipsel-linux-gnu, TARGET=MIPS1004K)	8m 36s
cross_build (alpha, alpha-linux-gnu, TARGET=EV4)	8m 4s
msys2 (UCRT64, int32, None, mingw-w64-ucrt-x86_64, fc)	1h 28m 58s
cross_build (riscv64, riscv64-linux-gnu, TARGET=RISCV64_GENERIC)	7m 39s
	11h 56m 3s

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