Returns the operating system and the CPU architecture that the running
R reports with base::Sys.info(), as a single string,
"<OS>-<architecture>". install_micromamba() uses it to choose the
micromamba build.
Value
A character string such as "Linux-x86_64", "Linux-aarch64",
"Darwin-x86_64" or "Darwin-arm64". On Windows it is
"Windows-aarch64" for a native ARM64 build of R. It is
"Windows-x86-64" for an x64 build, also when that build runs through
x64 emulation on an ARM64 PC.