Bug: Firmware does not build if submodule

[jlecoeur]

Bug Report

If PX4/Firmware is cloned as a submodule, it does not build.
I also had the problem when upgrading an existing Firmware submodule.

Steps to reproduce:

$ mkdir -p tmp/repo
$ cd tmp/repo
$ git init
$ git submodule add https://github.com/PX4/Firmware
$ git commit -am "Added submodule"
$ cd Firmware
$ git submodule update --init --recursive
$ make

-- Build Type: RelWithDebInfo
-- PX4 VERSION: v1.6.5-1632-gcf7140526
-- CONFIG: posix_sitl_default
-- The CXX compiler identification is GNU 7.2.0
-- The C compiler identification is GNU 7.2.0
-- The ASM compiler identification is GNU
-- Found assembler: /usr/bin/cc
-- 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
-- Found PythonInterp: /usr/bin/python (found version "3.6.3") 
-- Found PY_jinja2: /usr/lib/python3.6/site-packages/jinja2  
-- C compiler: cc (GCC) 7.2.0
-- C++ compiler: c++ (GCC) 7.2.0
CMake Error at src/lib/version/CMakeLists.txt:50 (message):
  /home/jlecoeur/tmp/repo/Firmware/src/lib/.git/modules/Firmware is not a
  directory


-- Configuring incomplete, errors occurred!
See also "/home/jlecoeur/tmp/repo/Firmware/build/posix_sitl_default/CMakeFiles/CMakeOutput.log".
/bin/sh: line 0: cd: /home/jlecoeur/tmp/repo/Firmware/build/posix_sitl_default: No such file or directory
make: *** [Makefile:147: posix_sitl_default] Error 1

When cloned separately, it works as expected:

$ mkdir tmp
$ git clone https://github.com/PX4/Firmware
$ cd Firmware
$ git submodule update --init --recursive
$ make

[dagar]

Thanks for reporting, we keep breaking this. Once we get it working again let's add something to CI.

[dagar]

Fixed in #8334