Fixes in build systems for autotools and cmake, see Issue 438

Thanks to Daniel KO Listas at the ODE mailing list
Don't build graphics demos when OpenGL or GLUT is not found
CMake will still build the non-graphical HelloWorld demo (output text to console)

Fix linker error: ThreadingDemo requires pthreads on UNIX systems
Thanks to reptor, see also http://bulletphysics.org/Bullet/phpBB3/posting.php?mode=reply&f=9&t=5748

Demos/CMakeLists.txt

@@ -3,51 +3,56 @@ IF (USE_DX11)
 	SUBDIRS(DX11ClothDemo)
 ENDIF()
 
+SUBDIRS( HelloWorld )
+
+
 IF (USE_GLUT)
-
-IF(BUILD_CPU_DEMOS)
-	SET(SharedDemoSubdirs
-		OpenGL AllBulletDemos  ConvexDecompositionDemo HelloWorld
-		CcdPhysicsDemo ConstraintDemo SliderConstraintDemo GenericJointDemo Raytracer
-		RagdollDemo ForkLiftDemo BasicDemo Box2dDemo BspDemo MovingConcaveDemo VehicleDemo
-		UserCollisionAlgorithm CharacterDemo SoftDemo HeightFieldFluidDemo
-		CollisionInterfaceDemo ConcaveConvexcastDemo SimplexDemo DynamicControlDemo
-		DoublePrecisionDemo ConcaveDemo CollisionDemo
-		ContinuousConvexCollision ConcaveRaycastDemo GjkConvexCastDemo
-		MultiMaterialDemo SerializeDemo InternalEdgeDemo 
-	)
-ELSE()
-	SET(SharedDemoSubdirs
-		OpenGL
-	)
-ENDIF()
-
-	SUBDIRS( 		${SharedDemoSubdirs}
-	Benchmarks
-		ThreadingDemo
-		MultiThreadedDemo
-		VectorAdd_OpenCL
-		ParticlesOpenCL
-		OpenCLClothDemo
+	IF (GLUT_FOUND)
+		IF(BUILD_CPU_DEMOS)
+			SET(SharedDemoSubdirs
+			OpenGL AllBulletDemos  ConvexDecompositionDemo
+			CcdPhysicsDemo ConstraintDemo SliderConstraintDemo GenericJointDemo Raytracer
+			RagdollDemo ForkLiftDemo BasicDemo Box2dDemo BspDemo MovingConcaveDemo VehicleDemo
+			UserCollisionAlgorithm CharacterDemo SoftDemo HeightFieldFluidDemo
+			CollisionInterfaceDemo ConcaveConvexcastDemo SimplexDemo DynamicControlDemo
+			DoublePrecisionDemo ConcaveDemo CollisionDemo
+			ContinuousConvexCollision ConcaveRaycastDemo GjkConvexCastDemo
+			MultiMaterialDemo SerializeDemo InternalEdgeDemo 
+			)
+		ELSE()
+			SET(SharedDemoSubdirs
+			OpenGL
 		)
+		ENDIF()
 
+		SUBDIRS( 		
+			${SharedDemoSubdirs}
+			Benchmarks
+			ThreadingDemo
+			MultiThreadedDemo
+			VectorAdd_OpenCL
+			ParticlesOpenCL
+			OpenCLClothDemo
+		)
+	ENDIF(GLUT_FOUND)
 ELSE (USE_GLUT)
+	IF (WIN32)
+		SUBDIRS( 
+		OpenGL 
+		BasicDemo 
+		Benchmarks 
+		Box2dDemo 
+		CollisionInterfaceDemo 
+		ConcaveDemo 
+		ConstraintDemo 
+		ConvexDecompositionDemo 
+		InternalEdgeDemo
+		GimpactTestDemo 
+		GenericJointDemo 
+		SerializeDemo 
+		SoftDemo
+		VectorAdd_OpenCL
+	)
+	ENDIF(WIN32)
+ENDIF (USE_GLUT)
 
-SUBDIRS( 
-	OpenGL 
-	BasicDemo 
-	Benchmarks 
-	Box2dDemo 
-	CollisionInterfaceDemo 
-	ConcaveDemo 
-	ConstraintDemo 
-	ConvexDecompositionDemo 
-	InternalEdgeDemo
-	GimpactTestDemo 
-	GenericJointDemo 
-	SerializeDemo 
-	SoftDemo
-	VectorAdd_OpenCL
-)
-
-ENDIF (USE_GLUT)