Backport runtime CPU detection from trunk in revisions: r186789,r186795,r186855,r1873...
tree8e651ce597592491c37760947d65e03d5254a9c4
drwxr-xr-x - gcc-4_6-mobile
drwxr-xr-x - gcc-4_6
drwxr-xr-x - gcc-4_6_2-mobile
drwxr-xr-x - gcc-4_6_3-mobile
drwxr-xr-x - gcc-4_7-integration
drwxr-xr-x - gcc-4_7-mobile
drwxr-xr-x - gcc-4_7
drwxr-xr-x - integration
drwxr-xr-x - main