fix simulation code compilation on Windows

- use g++ to link the executable on Windows with -static-libstc++
- remove c++ includes from the
  SimulationRuntime/c/simulation/simulation_runtime.h
- guard some files with extern "C" so we can always
  use g++ to compile the generated code

Belonging to [master]:
  - #2569

Author: adrpo

Compiler/Template/CodegenC.tpl

@@ -110,6 +110,7 @@ end translateModel;
     /* Simulation code for <%dotPath(modelInfo.name)%> generated by the OpenModelica Compiler <%getVersionNr()%>. */
     #if !defined(<%modelNamePrefixStr%>__MODEL_H)
     #define <%modelNamePrefixStr%>__MODEL_H
+
     #include "openmodelica.h"
     #include "openmodelica_func.h"
     #include "simulation_data.h"
@@ -122,6 +123,10 @@ end translateModel;
     #include "simulation/solver/nonlinearSystem.h"
     #include "simulation/solver/mixedSystem.h"
 
+    #if defined(__cplusplus)
+    extern "C" {
+    #endif
+
     #include <string.h>
 
     #include "<%fileNamePrefix%>_functions.h"
@@ -200,7 +205,12 @@ end translateModel;
       #define omp_get_max_threads() 1
     #endif
 
+    #if defined(__cplusplus)
+    }
     #endif
+
+    #endif /* !defined(<%modelNamePrefixStr%>__MODEL_H) */
+
     <%\n%>
     >>
   end match
@@ -1021,6 +1031,11 @@ template simulationFile(SimCode simCode, String guid, String isModelExchangeFMU)
       >>
     <<
     /* Main Simulation File */
+
+    #if defined(__cplusplus)
+    extern "C" {
+    #endif
+
     <%simulationFileHeader(simCode.fileNamePrefix)%>
     #include "simulation/solver/events.h"
 
@@ -1038,9 +1053,6 @@ template simulationFile(SimCode simCode, String guid, String isModelExchangeFMU)
     /* dummy VARINFO and FILEINFO */
     const FILE_INFO dummyFILE_INFO = omc_dummyFileInfo;
     const VAR_INFO dummyVAR_INFO = omc_dummyVarInfo;
-    #if defined(__cplusplus)
-    extern "C" {
-    #endif
 
     <%functionInput(simCode, modelInfo, modelNamePrefixStr)%>
 
@@ -1127,10 +1139,6 @@ template simulationFile(SimCode simCode, String guid, String isModelExchangeFMU)
 
     <%functionInitializeDataStruc(modelInfo, fileNamePrefix, guid, delayedExps, modelNamePrefixStr, isModelExchangeFMU)%>
 
-    #ifdef __cplusplus
-    }
-    #endif
-
     static int rml_execution_failed()
     {
       fflush(NULL);
@@ -1165,6 +1173,11 @@ template simulationFile(SimCode simCode, String guid, String isModelExchangeFMU)
       EXIT(res);
       return res;
     }
+
+    #ifdef __cplusplus
+    }
+    #endif
+
     <%\n%>
     >>
     %>
@@ -5774,7 +5787,7 @@ case SIMCODE(modelInfo=MODELINFO(varInfo=varInfo as VARINFO(__)), delayedExps=DE
   # Makefile generated by OpenModelica
 
   # Simulations use -O3 by default
-  CC=<%if boolOr(Flags.isSet(Flags.PARMODAUTO),acceptParModelicaGrammar()) then 'g++' else '<%makefileParams.ccompiler%>'%>
+  CC=<%if boolOr(boolOr(Flags.isSet(Flags.PARMODAUTO),acceptParModelicaGrammar()), boolOr(stringEq(makefileParams.platform, "win32"),stringEq(makefileParams.platform, "win64"))) then 'g++' else '<%makefileParams.ccompiler%>'%>
   CXX=<%makefileParams.cxxcompiler%>
   LINK=<%makefileParams.linker%>
   EXEEXT=<%makefileParams.exeext%>

SimulationRuntime/c/simulation/simulation_runtime.h

@@ -46,18 +46,15 @@
 #include <stdlib.h>
 #include <string.h>
 
-#ifdef __cplusplus
-#include <string>
-
 #include "linearization/linearize.h"
 #include "simulation/results/simulation_result.h"
 
+#ifdef __cplusplus
 extern "C" {
+#endif /* cplusplus */
 
 extern int initializeResultData(DATA* simData, threadData_t *threadData, int cpuTime);
 
-#endif /* cplusplus */
-
 extern int modelTermination;     /* Becomes non-zero when simulation terminates. */
 extern int terminationTerminate; /* Becomes non-zero when user terminates simulation. */
 extern int terminationAssert;    /* Becomes non-zero when model call assert simulation. */