Fix warning around "#pragma omp simd" usage that is not available on …

…Apple M1 Pro with Apple clang version 16.0.0 compiler:

[ 91%] Building CXX object modules/ar/CMakeFiles/visp_ar.dir/src/panda3d-simulator/vpPanda3DGeometryRenderer.cpp.o
.../modules/ar/src/panda3d-simulator/vpPanda3DGeometryRenderer.cpp:184:33: warning: loop not vectorized: the optimizer was unable to perform the requested transformation; the transformation might be disabled or specified as part of an unsupported transformation ordering [-Wpass-failed=transform-warning]
  184 | void vpPanda3DGeometryRenderer::getRender(vpImage<vpRGBf> &normals, vpImage<float> &depth, const vpRect &bb, unsigned int h, unsigned w) const
      |                                 ^
1 warning generated.

modules/ar/src/panda3d-simulator/vpPanda3DGeometryRenderer.cpp

@@ -198,16 +198,22 @@ void vpPanda3DGeometryRenderer::getRender(vpImage<vpRGBf> &normals, vpImage<floa
   if (numComponents != 4) {
     throw vpException(vpException::dimensionError, "Expected panda texture to have 4 components!");
   }
+
+  int image_width = static_cast<int>(m_renderParameters.getImageWidth());
   for (unsigned int i = 0; i < m_renderParameters.getImageHeight(); ++i) {
     const float *const rowData = data - i * rowIncrement;
     vpRGBf *normalRow = normals[top + i];
     float *depthRow = depth[top + i];
-#pragma omp simd
-    for (unsigned int j = 0; j < m_renderParameters.getImageWidth(); ++j) {
-      normalRow[left + j].R = (rowData[j * 4]);
-      normalRow[left + j].G = (rowData[j * 4 + 1]);
-      normalRow[left + j].B = (rowData[j * 4 + 2]);
-      depthRow[left + j] = (rowData[j * 4 + 3]);
+#if defined(_OPENMP)
+#pragma omp parallel for
+#endif
+    for (int j = 0; j < image_width; ++j) {
+      int left_j = left + j;
+      int j_4 = j + 4;
+      normalRow[left_j].R = (rowData[j_4]);
+      normalRow[left_j].G = (rowData[j_4 + 1]);
+      normalRow[left_j].B = (rowData[j_4 + 2]);
+      depthRow[left_j] = (rowData[j_4 + 3]);
     }
   }
 }