*while building the gr-osmosdr i received a bulk of errors* *I'm using Ubuntu 18.4 and gnuradio v3.9.*

*The following are the errors*

-- The CXX compiler identification is GNU 7.4.0 -- The C compiler identification is GNU 7.4.0 -- Check for working CXX compiler: /usr/bin/c++ -- Check for working CXX compiler: /usr/bin/c++ -- works -- Detecting CXX compiler ABI info -- Detecting CXX compiler ABI info - done -- Detecting CXX compile features -- Detecting CXX compile features - done -- Check for working C compiler: /usr/bin/cc -- Check for working C compiler: /usr/bin/cc -- works -- Detecting C compiler ABI info -- Detecting C compiler ABI info - done -- Detecting C compile features -- Detecting C compile features - done -- Build type not specified: defaulting to release. -- Found Git: /usr/bin/git (found version "2.17.1") -- Extracting version information from git describe... -- Configuring Boost C++ Libraries... -- Looking for pthread.h -- Looking for pthread.h - found -- Looking for pthread_create -- Looking for pthread_create - not found -- Looking for pthread_create in pthreads -- Looking for pthread_create in pthreads - not found -- Looking for pthread_create in pthread -- Looking for pthread_create in pthread - found -- Found Threads: TRUE -- Boost version: 1.65.1 -- Found the following Boost libraries: -- thread -- system -- chrono -- date_time -- atomic -- Found PkgConfig: /usr/bin/pkg-config (found version "0.29.1") -- Checking for module 'gruel' -- No package 'gruel' found -- Could NOT find GRUEL (missing: GRUEL_LIBRARIES GRUEL_INCLUDE_DIRS) -- Checking for module 'gnuradio-core' -- No package 'gnuradio-core' found -- Could NOT find GNURADIO_CORE (missing: GNURADIO_CORE_LIBRARIES GNURADIO_CORE_INCLUDE_DIRS) -- Checking for module 'gnuradio-iqbalance' -- Found gnuradio-iqbalance, version 0 -- Could NOT find GNURADIO_IQBALANCE (missing: GNURADIO_IQBALANCE_INCLUDE_DIRS) -- Checking for module 'uhd' -- No package 'uhd' found -- Could NOT find UHD (missing: UHD_LIBRARIES UHD_INCLUDE_DIRS) -- Checking for module 'gnuradio-uhd' -- Found gnuradio-uhd, version 3.9.0 -- gnuradio-uhd not found. -- Could NOT find GNURADIO_UHD (missing: GNURADIO_UHD_INCLUDE_DIRS) -- Checking for module 'gnuradio-fcd' -- No package 'gnuradio-fcd' found -- gnuradio-fcd not found. -- Could NOT find GNURADIO_FCD (missing: GNURADIO_FCD_LIBRARIES GNURADIO_FCD_INCLUDE_DIRS) -- Checking for module 'gnuradio-fcdproplus' -- Found gnuradio-fcdproplus, version 3.7.11 -- Found gnuradio-fcdproplus: /usr/include, /usr/lib/x86_64-linux-gnu/libgnuradio-fcdproplus.so -- Found GNURADIO_FCDPP: /usr/lib/x86_64-linux-gnu/libgnuradio-fcdproplus.so -- Checking for module 'libosmosdr' -- No package 'libosmosdr' found -- libosmosdr not found. -- Checking for module 'librtlsdr' -- No package 'librtlsdr' found -- librtlsdr not found. -- Checking for module 'libmirisdr' -- No package 'libmirisdr' found -- libmirisdr not found. -- Checking for module 'libhackrf' -- Found libhackrf, version 0.5 -- Found LIBHACKRF: /usr/local/lib/libhackrf.so -- Checking for module 'libairspy' -- No package 'libairspy' found -- Could NOT find LIBAIRSPY (missing: LIBAIRSPY_LIBRARIES LIBAIRSPY_INCLUDE_DIRS) -- Checking for module 'libbladeRF' -- No package 'libbladeRF' found -- libbladeRF not found. -- Could NOT find Doxygen (missing: DOXYGEN_EXECUTABLE) CMake Error at CMakeLists.txt:166 (message): Gruel required to build gr-osmosdr

-- Configuring incomplete, errors occurred! See also "/home/shan/gr-osmosdr/build/CMakeFiles/CMakeOutput.log". See also "/home/shan/gr-osmosdr/build/CMakeFiles/CMakeError.log".

*Thanks:)*