Fix compilation error in tutorials for linux

:Release Notes:
GLTF library contains implicit dependency from openmp.
Latest gcc version doesn't include openmp by default, so it is requried to bypass
-fopenmp flag to linkage

:Detailed Notes:

Fix error:
RadeonProRender/binUbuntu18/libProRenderGLTF.so: undefined reference to `omp_get_thread_num'
RadeonProRender/binUbuntu18/libProRenderGLTF.so: undefined reference to `omp_get_num_threads'
RadeonProRender/binUbuntu18/libProRenderGLTF.so: undefined reference to `omp_get_thread_num'
RadeonProRender/binUbuntu18/libProRenderGLTF.so: undefined reference to `omp_get_num_threads'
RadeonProRender/binUbuntu18/libProRenderGLTF.so: undefined reference to `GOMP_parallel'
RadeonProRender/binUbuntu18/libProRenderGLTF.so: undefined reference to `GOMP_parallel'

:Testing Performed:
Compilation and run at gentoo linux

:QA Notes:

:Issues Addressed:

Signed-off-by: Maksym Sditanov <msditanov@200volts.com>

Author: feniksa

tutorials/60_mesh_export/premake4.lua

@@ -12,9 +12,13 @@ project "60_mesh_export"
 
     buildoptions "-std=c++11"
 
-	configuration {"x64"}
-	links {"RadeonProRender64", "RprLoadStore64", "ProRenderGLTF"}
-	
+    configuration {"x64"}
+    links {"RadeonProRender64", "RprLoadStore64", "ProRenderGLTF"}
+
+    if os.istarget("linux") then
+        linkoptions "-fopenmp"
+    end
+
     configuration {"x64", "Debug"}
         targetdir "../Bin"
     configuration {"x64", "Release"}

tutorials/61_mesh_import/premake4.lua

@@ -12,9 +12,13 @@ project "61_mesh_import"
 
     buildoptions "-std=c++11"
 
-	configuration {"x64"}
-	links {"RadeonProRender64", "RprLoadStore64", "ProRenderGLTF"}
-	
+    configuration {"x64"}
+    links {"RadeonProRender64", "RprLoadStore64", "ProRenderGLTF"}
+
+    if os.istarget("linux") then
+        linkoptions "-fopenmp"
+    end
+
     configuration {"x64", "Debug"}
         targetdir "../Bin"
     configuration {"x64", "Release"}