Facing issue with Cmake while running command ./ns3 configure --enable-examples
-- CCache is enabled. Precompiled headers are disabled by default.
-- Using default output directory /home/vboxuser/Desktop/networksim/ns-allinone-3.36/ns-3.36/build
-- find_external_library: SQLite3 was found.
-- GTK3 was found.
-- LibXML2 was found.
-- LibRT was found.
-- MPI was found.
-- GSL was found.
-- Processing contrib/opengym
-- protobuf_generate command not found -> use a local copy from /home/vboxuser/Desktop/networksim/ns-allinone-3.36/ns-3.36/contrib/opengym/protobuf-generate.cmake
-- Processing src/visualizer
-- Processing src/antenna
-- Processing src/aodv
-- Processing src/applications
-- Processing src/bridge
-- Processing src/brite
-- find_external_library: brite was found.
-- Processing src/buildings
-- Processing src/click
-- find_external_library: click was found.
-- Processing src/config-store
-- Processing src/core
-- Boost Units have been found.
-- Processing src/csma
-- Processing src/csma-layout
-- Processing src/dsdv
-- Processing src/dsr
-- Processing src/energy
-- Processing src/fd-net-device
-- Processing src/flow-monitor
-- Processing src/internet
-- Processing src/internet-apps
-- Processing src/lr-wpan
-- Processing src/lte
-- Processing src/mesh
-- Processing src/mobility
-- Processing src/mpi
-- Processing src/netanim
-- Processing src/network
-- Processing src/nix-vector-routing
-- Processing src/olsr
-- Processing src/openflow
-- find_external_library: openflow was found.
-- Processing src/point-to-point
-- Processing src/point-to-point-layout
-- Processing src/propagation
-- Processing src/sixlowpan
-- Processing src/spectrum
-- Processing src/stats
-- Processing src/tap-bridge
-- Processing src/test
-- Processing src/topology-read
-- Processing src/traffic-control
-- Processing src/uan
-- Processing src/virtual-net-device
-- Processing src/wave
-- Processing src/wifi
-- Processing src/wimax
-- ---- Summary of optional NS-3 features:
Build profile                 : debug
Build directory               : /home/vboxuser/Desktop/networksim/ns-allinone-3.36/ns-3.36/build
BRITE Integration             : ON
DES Metrics event collection  : OFF (not requested)
DPDK NetDevice                : OFF (not requested)
Emulation FdNetDevice         : ON
Examples                      : ON
File descriptor NetDevice     : ON
GNU Scientific Library (GSL)  : ON
GtkConfigStore                : ON
MPI Support                   : ON
NS-3 Click Integration        : ON
NS-3 OpenFlow Integration     : ON
Netmap emulation FdNetDevice  : OFF (missing dependency)
PyViz visualizer              : ON
Python Bindings               : ON
Real Time Simulator           : ON
SQLite stats support          : ON
Tap Bridge                    : ON
Tap FdNetDevice               : ON
Tests                         : ON
Modules configured to be built:
antenna                   aodv                      applications              
bridge                    brite                     buildings                 
click                     config-store              core                      
csma                      csma-layout               dsdv                      
dsr                       energy                    fd-net-device             
flow-monitor              internet                  internet-apps             
lr-wpan                   lte                       mesh                      
mobility                  mpi                       netanim                   
network                   nix-vector-routing        olsr                      
openflow                  opengym                   point-to-point            
point-to-point-layout     propagation               sixlowpan                 
spectrum                  stats                     tap-bridge                
test                      topology-read             traffic-control           
uan                       virtual-net-device        visualizer                
wave                      wifi                      wimax                     
-- Configuring done
CMake Error at scratch/CMakeLists.txt:47 (add_executable):
  Target "scratch_subdir_scratch-simulator-subdir" links to target
  "protobuf::libprotobuf" but the target was not found.  Perhaps a
  find_package() call is missing for an IMPORTED target, or an ALIAS target
  is missing?
Call Stack (most recent call first):
  scratch/CMakeLists.txt:97 (create_scratch)
CMake Error at scratch/CMakeLists.txt:47 (add_executable):
  Target "scratch_scratch-simulator" links to target "protobuf::libprotobuf"
  but the target was not found.  Perhaps a find_package() call is missing for
  an IMPORTED target, or an ALIAS target is missing?
Call Stack (most recent call first):
  scratch/CMakeLists.txt:67 (create_scratch)
CMake Error at scratch/CMakeLists.txt:47 (add_executable):
  Target "scratch_subdir_scratch-simulator-subdir" links to target
  "protobuf::libprotobuf" but the target was not found.  Perhaps a
  find_package() call is missing for an IMPORTED target, or an ALIAS target
  is missing?
Call Stack (most recent call first):
  scratch/CMakeLists.txt:97 (create_scratch)
CMake Error at scratch/CMakeLists.txt:47 (add_executable):
  Target "scratch_scratch-simulator" links to target "protobuf::libprotobuf"
  but the target was not found.  Perhaps a find_package() call is missing for
  an IMPORTED target, or an ALIAS target is missing?
Call Stack (most recent call first):
  scratch/CMakeLists.txt:67 (create_scratch)
-- Generating done
CMake Generate step failed.  Build files cannot be regenerated correctly.
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