Fix Linux build

Author: yozhijk

RadeonRays/RadeonRays.lua

@@ -34,13 +34,14 @@ project "RadeonRays"
 
     excludes {"../RadeonRays/src/device/embree*"}
     if os.is("macosx") then
-        buildoptions "-std=c++11 -stdlib=libc++"
+        buildoptions "-std=c++14 -stdlib=libc++"
         filter { "kind:SharedLib", "system:macosx" }
         linkoptions { '-Wl,-install_name', '-Wl,@loader_path/%{cfg.linktarget.name}' }
 
     elseif os.is("linux") then
-        buildoptions "-std=c++11 -fPIC"
+        buildoptions "-std=c++14 -msse4.2 -fPIC"
         linkoptions {"-Wl,--no-undefined"}
+	links {"pthread"}	
 
         --get API version from header.
         local handle = io.popen("grep -r RADEONRAYS_API_VERSION include/radeon_rays.h | cut -d \" \" -f 3")

RadeonRays/src/accelerator/bvh2.h

@@ -70,7 +70,7 @@ namespace RadeonRays
             // Max triangles per leaf
             kMaxLeafPrimitives = 1u,
             // Threshold number of primitives to disable SAH split
-            kMinSAHPrimitives = 32u,
+            kMinSAHPrimitives = 8u,
             // Maximum stack size for non-parallel builds
             kStackSize = 1024u
         };