RISCV64-CI: don't rely on dependency resolution for qemu-user #6247

Job	Run time
build (ubuntu-latest, flang, cmake)	11m 45s
msys2 (UCRT64, int32, Release)	16m 12s
build (ubuntu-latest, gfortran, make)	22m 9s
build (ubuntu-latest, flang, make)	19m 59s
msys2 (UCRT64, int64, Release)	14m 20s
cross_build (mips64el, mips64el-linux-gnuabi64, DYNAMIC_ARCH=1 TARGET=GENERIC)	3m 42s
build (macos-latest, gfortran, make)	5m 30s
neoverse_build	7m 46s
build (ubuntu-latest, gfortran, cmake)	12m 43s
build (macos-latest, gfortran, cmake)	22m 47s
msys2 (CLANG64, int32, Release)	17m 59s
msys2 (CLANG64, int64, Release)	16m 35s
msys2 (UCRT64, int32, None, mingw-w64-ucrt-x86_64, fc)	16m 14s
cross_build (riscv64, riscv64-linux-gnu, TARGET=RISCV64_GENERIC)	2m 36s
cross_build (mipsel, mipsel-linux-gnu, TARGET=MIPS1004K)	3m 39s
cross_build (alpha, alpha-linux-gnu, TARGET=EV4)	2m 45s
msys2 (MINGW32, int32, Release)	14m 59s
	3h 31m 40s

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