R help - May 2015 - Specifying Directory to Search When Updating a Package

R packages here are installed in /usr, not /usr/local/. Most of the time
when I run 'update.packages()' each finds headers in /usr/include.
Today,
the package 'rgl' failed to build because it was looking for freetype.h
in
/usr/local/include/freetype2/.

   By making a softlink from /usr/include/freetype2 to /usr/local/include/
the package update built without further error.

   For future reference, if an update attempt fails because the code is
looking in a different directory than where the required file (usually a
header) is found, is there a way to specify the correct directory when
issuing the update.packages() command?

Rich