[R] Allow statically linked libcurl in GCS when building libarrow DLL in RTools

[asfimport]

Neal's patch in ARROW-16510 enabled libcurl to be linked statically in the google cloud storage dependency, but this only seems to work for static libraries on RTools (Windows). For development Rtools environments, we currently use dynamic Arrow libraries instead, but currently we get linking errors to libcurl when ARROW_GCS is on.

Reporter: Will Jones / @wjones127

_{Note: This issue was originally created as ARROW-17150. Please see the migration documentation for further details.}

[github-actions]

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