Remove compiled objects from /src/ directory
Default compiler flags used by devtools.
Does the package need recompiling? (i.e. is there a source or header file newer than the dll)
Does a source package have src/ directory?
Test if a package path is linking to Rcpp or cpp11
Call R CMD 'command' with build tools active
Retrieve a text string with the rtools version needed
Temporarily set debugging compilation flags.