RISCV64-CI: don't rely on dependency resolution for qemu-user #6266

Job	Run time
msys2 (MINGW32, int32, Release)	15m 23s
msys2 (UCRT64, int32, Release)	16m 40s
cross_build (riscv64, riscv64-linux-gnu, TARGET=RISCV64_GENERIC)	2m 43s
cross_build (mips64el, mips64el-linux-gnuabi64, DYNAMIC_ARCH=1 TARGET=GENERIC)	4m 38s
cross_build (alpha, alpha-linux-gnu, TARGET=EV4)	2m 54s
cross_build (mipsel, mipsel-linux-gnu, TARGET=MIPS1004K)	3m 43s
msys2 (CLANG64, int64, Release)	21m 46s
build (ubuntu-latest, gfortran, cmake)	46m 21s
msys2 (CLANG64, int32, Release)	17m 40s
build (ubuntu-latest, gfortran, make)	23m 47s
msys2 (UCRT64, int32, None, mingw-w64-ucrt-x86_64, fc)	13m 43s
msys2 (UCRT64, int64, Release)	15m 15s
build (ubuntu-latest, flang, cmake)	13m 19s
build (ubuntu-latest, flang, make)	5m 30s
build (macos-latest, gfortran, make)	6m 6s
build (macos-latest, gfortran, cmake)	20m 7s
neoverse_build	8m 2s
	3h 57m 37s

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