fix: Link Fortran runtime on Windows as needed by arpack.

[kalibera]

Fortran libraries (Fortran runtime) is needed e.g. by arpack. This change is to fix building on LLVM/aarch64.

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[krlmlr]

Thanks. Do we need the same change in Makevars.win ?

[kalibera]

Thanks. Do we need the same change in Makevars.win ?

It would be probably cleaner to do so, because Fortran runtime is used. But you probably don't need it, certainly not for aarch64.

I am not sure if you need Makevars.win at all, maybe you could delete it and rename the current Makevars.ucrt to Makevars.win. That depends on how old versions of R you want to support (on CRAN).

Makevars.ucrt is used by R >= 4.2.0, when it exists. When it doesn't exist, R >= 4.2.0 uses Makevars.win as well as the older versions of R do (details are in Writing R Extensions).

At least with R >= 4.2.0 (and so Rtools >= 42), you don't even need to specify "-I" options for LIB_XML, GLPK_HOME, LIB_GMP, the R_TOOLS_SOFT directory is by default made available by the toolchain. So you might need a distinct Makevars.win only if you wanted to support R < 4.2 (with Rtools < 42).

[krlmlr]

Thanks for your input. I guess I'll go with "never touch a running system" with this respect, and adapt as needed on users's request.