Setting the "help" keyword argument may not fit in one line sometimes. This
patch adds the following convention to calls to add_option() in order to
address that issue in a better way:
1) The "help" keyword must always be the last argument to be passed.
2) If the help string is a literal string or a literal string with some
operation (e.g. "%" operator) and setting the "help" keyword in the code
doesn't fit a line (considering the limit of characters in a line), then
the help string must be a triple-quoted string. That has the advantage of
not having to have several "+" operations for long help strings. In that
case, the help message must start on the next line and the closing
triple-quotes must be on a separate line together with the closing
parenthesis.
The requirement (1) makes it easier to make the style exception in (2)
acceptable.
There's an upcoming patch that moves all static libraries to
`build/<board>/lib/`. That way, the program directory won't be created
automatically by the build system and that will cause problems for PX4 builds,
since it builds ardupilot programs as static libraries and copies stuff to the
program directory.
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
```
Create a new configuration task a configuration in the CMakeConfig object
changes. That allows building targets for different configurations in one waf
build run.
