Simply use a separate temp variable

The dynamic_cast thing caused error: dynamic_cast from rvalue to
reference type 'std::ostringstream &' (aka 'basic_ostringstream<char>
&') with Clang in C++11 mode.

Clearly putting the value of integer expressions into strings is a
very esoteric corner case that very few C++ programs need to do, if it
is this hard to do it and there is no obvious standard idiom that
would work in all compilers and language vintages.

Change-Id: I46ed2bd2a8f860d7323682b19886ec732b0722c1

sc/source/core/opencl/opencl_device.cxx

@@ -244,7 +244,9 @@ ds_status evaluateScoreForDevice(ds_device* device, void* evalData)
         bool bAmdFp64Flag = false;
         const char* buildOption = NULL;
         std::string tmpStr("-Dfp_t=double -Dfp_t4=double4 -Dfp_t16=double16 -DINPUTSIZE=");
-        tmpStr.append(dynamic_cast<std::ostringstream&>(std::ostringstream() << std::dec << INPUTSIZE).str());
+        std::ostringstream tmpOStrStr;
+        tmpOStrStr << std::dec << INPUTSIZE;
+        tmpStr.append(tmpOStrStr.str());
 
         if ((std::string(aExtInfo)).find("cl_khr_fp64") != std::string::npos)
         {