Hi

I am building "seL4test" using the Docker image on Ubuntu 18.04.3 LTS, a 64-bit system.  After entering "../init-build.sh -DPLATFORM=x86_64 -DSIMULATION=TRUE" in a build directory within Docker it complained "Could NOT find NANOPB (missing: PROTOBUF_PROTOC_EXECUTABLE)".  I wonder should I manually download and install protocol buffer compiler, protoc?

Please advise.

Thank for your help.

Jacob
===============================================
loading initial cache file /host/projects/sel4test/settings.cmake
correct_platform_strings: Attempting to correct PLATFORM: x86_64
            to new valid KernelPlatform: pc99
                         KernelSel4Arch: x86_64
-- Found seL4: /host/kernel  
-- The C compiler identification is GNU 6.5.0
-- The CXX compiler identification is GNU 6.5.0
-- The ASM compiler identification is GNU
-- Found assembler: /usr/bin/gcc
-- Check for working C compiler: /usr/bin/gcc
-- Check for working C compiler: /usr/bin/gcc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/bin/g++
-- Check for working CXX compiler: /usr/bin/g++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Found elfloader-tool: /host/tools/seL4/elfloader-tool  
-- Found musllibc: /host/projects/musllibc  
-- Found util_libs: /host/projects/util_libs  
-- Found seL4_libs: /host/projects/seL4_libs  
-- Found sel4_projects_libs: /host/projects/sel4_projects_libs  
-- Found sel4runtime: /host/projects/sel4runtime  
-- Performing Test compiler_arch_test
-- Performing Test compiler_arch_test - Success
-- Found PythonInterp: /usr/bin/python (found version "2.7.15")
-- Could NOT find NANOPB (missing: PROTOBUF_PROTOC_EXECUTABLE)
-- CPIO test cpio_reproducible_flag PASSED
-- Configuring done
-- Generating done
-- Build files have been written to: /host/build-x86