Merge pull request #4924 from XiWeiGu/la64_readme #5069

Job	Run time
build (ubuntu-latest, gfortran, cmake)	42m 0s
build (ubuntu-latest, gfortran, make)	16m 38s
build (ubuntu-latest, flang, cmake)	13m 21s
build (ubuntu-latest, flang, make)	7m 7s
build (macos-latest, gfortran, cmake)	14m 31s
build (macos-latest, gfortran, make)	6m 35s
cross_build (mips64el, mips64el-linux-gnuabi64, DYNAMIC_ARCH=1 TARGET=GENERIC)	5m 40s
msys2 (UCRT64, int32, Release)	15m 6s
cross_build (riscv64, riscv64-linux-gnu, TARGET=RISCV64_GENERIC)	4m 55s
msys2 (UCRT64, int64, Release)	17m 11s
cross_build (mipsel, mipsel-linux-gnu, TARGET=MIPS1004K)	5m 48s
msys2 (MINGW32, int32, Release)	18m 56s
cross_build (alpha, alpha-linux-gnu, TARGET=EV4)	4m 58s
msys2 (CLANG64, int32, Release)	15m 46s
msys2 (CLANG64, int64, Release)	18m 28s
msys2 (CLANG32, int32, Release)	10m 58s
msys2 (UCRT64, int32, None, mingw-w64-ucrt-x86_64, fc)	13m 32s
	3h 51m 30s

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