add 3dfx env variables

internal/rootfs/etc/environment

@@ -0,0 +1,18 @@
+SSTV2_FASTMEM_RAS_READS=1
+SSTV2_FASTMEM_READ=1
+SSTV2_FASTMEM=1
+SSTV2_FASTPCIRD=1
+SSTV2_GRXCLK=90
+SSTV2_SLIM_VOUT_CLKDEL=0
+SSTV2_SLIM_VIN_CLKDEL=0
+SSTV2_SLIS_VOUT_CLKDEL=0
+SSTV2_SLIS_VIN_CLKDEL=0
+SSTV2_SWAPINTERVAL=0
+FX_GLIDE_SWAPINTERVAL=0
+SSTV2_GAMMA=1.3
+SSTV2_MISMATCHED_SLI=1
+SSTV2_SWAP_EN_WAIT_ON_VSYNC=0
+SSTV2_SCREENREFRESH=75
+FX_GLIDE_SHAMELESS_PLUG=1
+MESA_GLX_FX=f
+MESA_FX_INFO=1