internalize loadTransform(RTCFormat, const float*) (#559)

loadTransform(RTCFormat, const float*) is an implementation detail of
rtcore.cpp, so it should be declared as `static` to prevent it from
being exported from static library builds.

Co-authored-by: Stefan Werner <stefan.werner@intel.com>

Author: timblechmann

kernels/common/rtcore.cpp

@@ -1405,7 +1405,7 @@ RTC_NAMESPACE_BEGIN;
     RTC_CATCH_END2(geometry);
   }
 
-  AffineSpace3fa loadTransform(RTCFormat format, const float* xfm)
+  static AffineSpace3fa loadTransform(RTCFormat format, const float* xfm)
   {
     AffineSpace3fa space = one;
     switch (format)