add build flann externalproject

CMakeLists.txt

@@ -23,6 +23,7 @@ option(AV_BUILD_VPX "Enable building an embedded libvpx required for ffmpeg" ON)
 option(AV_BUILD_COINUTILS "Enable building an embedded CoinUtils" ON)
 option(AV_BUILD_OSI "Enable building an embedded Osi" ON)
 option(AV_BUILD_CLP "Enable building an embedded Clp" ON)
+option(AV_BUILD_FLANN "Enable building an embedded Flann" ON)
 option(AV_BUILD_PCL "Enable building an embedded PointCloud library" ON)
 option(AV_BUILD_USD "Enable building an embedded USD library" OFF)
 option(AV_BUILD_ALICEVISION "Enable building of AliceVision" ON)
@@ -976,9 +977,7 @@ ExternalProject_Add(${CLP_TARGET}
 set(CLP_CMAKE_FLAGS -DClp_DIR:PATH=${CMAKE_INSTALL_PREFIX}/share/clp)
 endif()
 
-# Add PCL
-if(AV_BUILD_PCL)
- # build other dependencies for pcl
+if(AV_BUILD_FLANN)
  # add lz4 for flann
  set(LZ4_TARGET lz4)
  ExternalProject_Add(${LZ4_TARGET}
@@ -998,12 +997,10 @@ if(AV_BUILD_PCL)
  )
  set(LZ4_CMAKE_FLAGS -Dlz4_DIR:PATH=${CMAKE_INSTALL_PREFIX}/lib/cmake/lz4/)
 
- # @TODO whenever flann will be removed as embedded dependency move this and lz4 out from if(AV_BUILD_PCL) as they will be needed by the library
- # add flann
  set(FLANN_TARGET flann)
  ExternalProject_Add(${FLANN_TARGET}
  GIT_REPOSITORY https://github.com/alicevision/flann
- GIT_TAG 9e79ca6881b779fb842e83c17aef1f4c816ce058
+ GIT_TAG 46e72429ef60ce9c413fa926ac7729f8dee96395
  PREFIX ${BUILD_DIR}
  BUILD_IN_SOURCE 0
  BUILD_ALWAYS 0
@@ -1025,6 +1022,10 @@ if(AV_BUILD_PCL)
  )
  set(FLANN_CMAKE_FLAGS -Dflann_DIR:PATH=${CMAKE_INSTALL_PREFIX}/lib/cmake/flann/)
 
+endif()
+
+# Add PCL
+if(AV_BUILD_PCL)
  # add point cloud library
  set(PCL_TARGET pcl)
  ExternalProject_Add(${PCL_TARGET}