A (possible) bug in CMake makes it not to relink firmware_nuttx sometimes when
the following sequence of events happen with very short period of time in
between them:
1) cmake target build_firmware_px4fmu-v2 just finishes
2) px4-extra-files/libap_program.a is replaced with the next library
3) cmake target build_firmware_px4fmu-v2 is run
It's unfortunate to have to reconfigure PX4Firmware with a different path
because of the overhead added.
That problem was found with CMake 3.5.2 and is reproducible with the following
bash script (with git HEAD at ae3cb05 'HAL_PX4: disable "Overtime in task"
msg'):
```
modules/waf/waf-light configure --board px4-v2
modules/waf/waf-light build --targets bin/arduplane,bin/arducopter-quad
fails=0
total=0
while true; do
cp build/px4-v2/bin/libarducopter-quad.a \
build/px4-v2/px4-extra-files/libap_program.a
cmake --build build/px4-v2/modules/PX4Firmware \
--target build_firmware_px4fmu-v2 &> /dev/null
h1=$(sha256sum build/px4-v2/modules/PX4Firmware/src/firmware/nuttx/firmware_nuttx \
| cut -d" " -f1)
cp build/px4-v2/bin/libarduplane.a build/px4-v2/px4-extra-files/libap_program.a
cmake --build build/px4-v2/modules/PX4Firmware \
--target build_firmware_px4fmu-v2 &> /dev/null
h2=$(sha256sum build/px4-v2/modules/PX4Firmware/src/firmware/nuttx/firmware_nuttx \
| cut -d" " -f1)
[[ $h1 == $h2 ]] && ((fails++))
((total++))
printf "\r%d/%d" $fails $total
done
```
Files that are not really part of the ROMFS in the folder might cause problems.
One problem that motivated this patch was caused because the make-based build
system copies the bootloader to the ROMFS in the source tree (mk/PX4/ROMFS)
instead of the build tree. That potentially could cause race condition between
the tasks created by 'px4_romfs_static_files' and 'px4_romfs_bootloader'.
Also, now we have only one task generator for static files.
That way we don't force other programs to be built on a directory of their
program group name. The directory name defaults to the program group.
We are separating those two concepts because of the upcoming support for
multiple groups for a program.
Copy the program library to the place where PX4Firmware CMake build will look
for and trigger the firmware build. There isn't really a real output defined
for px4_copy_lib because Waf would complain about multiple tasks having same
output when building multiple programs.
After the firmware build, copy it to the correct place (from program group and
name perspective) and add git hashes.
Since the place where the library is placed is shared by different target
programs, we need to synchronize the firmware build, that's why the use of
_firmware_semaphorish_tasks. That variable is set as a list because of the
upcoming upload task.
Recursively collect objects from dependency libraries and create a single
library. That way we just need to pass down one single library to PX4Firmware
build system.
Gustavo Jose de Sousa
Andrew Tridgell
Lucas De Marchi
Francisco Ferreira