[R-SIG-Mac] new compilers from Apple

[Jan de Leeuw]

The following setup on SL compiles R-devel and passes check.

  C compiler:                /Developer/usr/bin/llvm-gcc -std=gnu99 -m64 -O4 -Wall -fopenmp -mtune=native
  Fortran 77 compiler:       /usr/local/bin/gfortran-4.5 -m64 -O4 -Wall -fopenmp -mtune=native
  C++ compiler:              /Developer/usr/bin/llvm-g++ -m64 -O4 -Wall -fopenmp -mtune=native
  Fortran 90/95 compiler:    /usr/local/bin/gfortran-4.5 -m64 -O4 -Wall -fopenmp -mtune=native
  Obj-C compiler:	     /Developer/usr/bin/llvm-gcc -m64 -O4 -Wall -fopenmp -mtune=native

This compiles at breakneck speed (compared to gcc-4.2 or gcc-4.5). In fact, with recommended packages, 
for all of R-devel:

time make -j8 
real	2m33.028s
user	3m59.076s
sys	0m33.248s

NB: I still have problems with CC and OBJC equal to clang (from Apple) 
or to clang (from the llvm svn), even without the -fopenmp flag. 

===============================================================
     Jan de Leeuw, 11667 Steinhoff Rd, Frazier Park, CA 93225
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