error: ‘gflags’ has not been declared

[Yuchy-Zhao]

I have install gflags by:

sudo apt-get install -y libgoogle-glog-dev libgtest-dev libgflags-dev python3-dev libsqlite3-dev
cd /usr/src/googletest && sudo cmake . && sudo cmake --build . --target install

But still found:
/home/yuchy/Dev/nvblox/nvblox/executables/include/nvblox/gflags_param_loading/fuser_params_from_gflags.h: In function ‘void nvblox::get_multi_mapper_params_from_gflags(float*, nvblox::MappingType*, nvblox::EsdfMode*, nvblox::MultiMapper::Params*)’:
/home/yuchy/Dev/nvblox/nvblox/executables/include/nvblox/gflags_param_loading/fuser_params_from_gflags.h:96:8: error: ‘gflags’ has not been declared
96 | if (!gflags::GetCommandLineFlagInfoOrDie("voxel_size").is_default) {
| ^~~~~~
/home/yuchy/Dev/nvblox/nvblox/executables/include/nvblox/gflags_param_loading/fuser_params_from_gflags.h:102:8: error: ‘gflags’ has not been declared
102 | if (!gflags::GetCommandLineFlagInfoOrDie("mapping_type_static_occupancy")
| ^~~~~~
/home/yuchy/Dev/nvblox/nvblox/executables/include/nvblox/gflags_param_loading/fuser_params_from_gflags.h:110:8: error: ‘gflags’ has not been declared
110 | if (!gflags::GetCommandLineFlagInfoOrDie("mapping_type_dynamic").is_default) {
| ^~~~~~
/home/yuchy/Dev/nvblox/nvblox/executables/include/nvblox/gflags_param_loading/fuser_params_from_gflags.h:119:8: error: ‘gflags’ has not been declared
119 | if (!gflags::GetCommandLineFlagInfoOrDie("use_2d_esdf_mode").is_default) {
| ^~~~~~
/home/yuchy/Dev/nvblox/nvblox/executables/include/nvblox/gflags_param_loading/fuser_params_from_gflags.h:124:8: error: ‘gflags’ has not been declared
124 | if (!gflags::GetCommandLineFlagInfoOrDie("esdf_2d_min_height").is_default) {
| ^~~~~~
/home/yuchy/Dev/nvblox/nvblox/executables/include/nvblox/gflags_param_loading/fuser_params_from_gflags.h:129:8: error: ‘gflags’ has not been declared
129 | if (!gflags::GetCommandLineFlagInfoOrDie("esdf_2d_max_height").is_default) {
| ^~~~~~
/home/yuchy/Dev/nvblox/nvblox/executables/include/nvblox/gflags_param_loading/fuser_params_from_gflags.h:134:8: error: ‘gflags’ has not been declared
134 | if (!gflags::GetCommandLineFlagInfoOrDie("esdf_slice_height").is_default) {
| ^~~~~~
/home/yuchy/Dev/nvblox/nvblox/executables/include/nvblox/gflags_param_loading/fuser_params_from_gflags.h:139:8: error: ‘gflags’ has not been declared
139 | if (!gflags::GetCommandLineFlagInfoOrDie(
| ^~~~~~

It seems that nvblox has not found gflags installed.
Could you help me why this error ocurred?
My system is Ubuntu 20.04 with cuda 11.7