Changes

Update Makefile to allow building i965_dri.so with disabled shader cache

It turned out that the file "/usr/lib/xorg/modules/dri/amd64/i965_dri.so" is missing because the "brw_disk_cache_init" function causes X to crash. Disabling the shader disk cache makes "i965_dri.so" work, so I propose disabling this cache and enabling "i965_dri.so". For more info see https://daemonforums.org/showthread.php?t=12745#post75889
 (commit: 91cfc08)