[ci] reduce hard-coding of host architecture #8194

Job	Run time
r-package (ubuntu-latest, gcc, R 3.6, cmake)	8m 46s
r-package (ubuntu-latest, gcc, R 4.3, cmake)	9m 39s
r-package (ubuntu-latest, clang, R 3.6, cmake)	8m 52s
r-package (ubuntu-latest, clang, R 4.3, cmake)	10m 22s
r-package (macOS-latest, gcc, R 4.3, cmake)	26m 45s
r-sanitizers (ubuntu-latest, R-devel, gcc ASAN/UBSAN)	15m 36s
r-package (macOS-latest, clang, R 4.3, cmake)	12m 1s
r-sanitizers (ubuntu-latest, R-devel, clang ASAN/UBSAN)	32m 1s
r-package (windows-latest, MINGW, R 3.6, cmake)	12m 36s
r-package (windows-latest, MINGW, R 4.3, cmake)	14m 12s
r-package (windows-2019, MSVC, R 3.6, cmake)	10m 21s
r-package (debian, R-devel, clang-16)	16m 5s
r-package (windows-2022, MSVC, R 4.3, cmake)	25m 39s
r-package (debian, R-devel, clang-17)	16m 55s
r-package (windows-latest, MINGW, R 3.6, cran)	18m 9s
r-package (windows-latest, MINGW, R 4.3, cran)	20m 18s
r-package (ubuntu-latest, gcc, R 4.3, cran)	15m 17s
r-package (macOS-latest, clang, R 4.3, cran)	21m 0s
r-rchk (ubuntu-latest, gcc, R 4.3, cran)	10m 7s
all-r-package-jobs-successful	2s
	5h 4m 43s

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