[R-SIG-Mac] How to workaround RStudio issues

[Duncan Murdoch]

RStudio is causing problems for rgl builds.  In particular, on my M3 
system, I have installed the arm64 binaries and tools in 
/opt/R/arm64/bin as recommended, and builds work fine if I run them in a 
shell with that directory first in the PATH.

However, when I try to do builds in RStudio, they fail.  I think this is 
because it prepends /usr/local/bin to my PATH before configuring, and 
the rgl configure script finds the x86_64 versions of some files before 
the arm64 ones, and they don't work.  So then rgl thinks I don't have 
X11 libs available, and builds as though I don't.

This isn't the right place to ask how to fix RStudio.  I've already done 
that in one of their forums, and I already know how to build rgl outside 
of it.  However, I do get complaints from users who try to build rgl and 
have the builds fail (e.g. https://github.com/dmurdoch/rgl/issues/423), 
and I'd like to make the configure script resilient against this sort of 
problem.  (And this might not be RStudio specific:  there are lots of 
ways to end up with a PATH that doesn't have things in the right order.)

So here are my questions:

  - What is the correct way in a package configure script (or 
configure.ac, since I use autoconf) to determine that the build is 
happening on an arm64 Mac?

  - Is it correct in a configure script to force the arm64 directory to 
be first?  If so, how do I do that?

  - How do I determine if the user really did install the arm64 files to 
/opt/R/arm64/bin?

  - Should I really be doing this, or is my system broken since my 
/usr/local/bin directory contains things it shouldn't, or should I just 
tell people to put /opt/R/arm64/bin first in their PATH?

Duncan Murdoch