Fix #5521: add @SUFFIX64@ in OpenBLASConfig.cmake.in #6256

Job	Run time
cross_build (mipsel, mipsel-linux-gnu, TARGET=MIPS1004K)	3m 35s
cross_build (alpha, alpha-linux-gnu, TARGET=EV4)	3m 50s
msys2 (MINGW32, int32, Release)	16m 9s
build (ubuntu-latest, gfortran, make)	21m 26s
cross_build (riscv64, riscv64-linux-gnu, TARGET=RISCV64_GENERIC)	3m 15s
msys2 (CLANG64, int64, Release)	18m 22s
build (macos-latest, gfortran, make)	4m 29s
neoverse_build	8m 6s
msys2 (UCRT64, int32, Release)	15m 53s
cross_build (mips64el, mips64el-linux-gnuabi64, DYNAMIC_ARCH=1 TARGET=GENERIC)	3m 49s
msys2 (CLANG64, int32, Release)	17m 32s
msys2 (UCRT64, int64, Release)	15m 44s
build (macos-latest, gfortran, cmake)	18m 25s
build (ubuntu-latest, flang, make)	6m 37s
build (ubuntu-latest, flang, cmake)	44m 55s
msys2 (UCRT64, int32, None, mingw-w64-ucrt-x86_64, fc)	13m 43s
build (ubuntu-latest, gfortran, cmake)	44m 50s
	4h 20m 40s

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