this adds non-turbulent wind support for the built-in simulators. I
added it primarily for quadplane testing, but it should also be useful
for multicopter navigation testing.
In several places we use functions like asprintf() that are only
available in libc when _GNU_SOURCE is defined. Always define _GNU_SOURCE
since we always want to use them.
This fixes the build on Windows using cygwin.
Otherwise it fails to link:
[335/335] Linking build/sitl/bin/arducopter-quad.exe
ArduCopter/libArduCopter_libs.a(SIM_Aircraft.cpp.4.o):SIM_Aircraft.cpp:(.text$_ZN4SITL8AircraftC2EPKcS2_+0x230): undefined reference to `_imp__timeGetTime@0'
ArduCopter/libArduCopter_libs.a(SIM_Aircraft.cpp.4.o):SIM_Aircraft.cpp:(.text$_ZN4SITL8Aircraft16setup_frame_timeEff+0x9f): undefined reference to `_imp__timeGetTime@0'
ArduCopter/libArduCopter_libs.a(SIM_Aircraft.cpp.4.o):SIM_Aircraft.cpp:(.text$_ZN4SITL8Aircraft16setup_frame_timeEff+0x125): undefined reference to `_imp__timeGetTime@0'
ArduCopter/libArduCopter_libs.a(SIM_Aircraft.cpp.4.o):SIM_Aircraft.cpp:(.text$_ZN4SITL8Aircraft15sync_frame_timeEv+0x21): undefined reference to `_imp__timeGetTime@0'
ArduCopter/libArduCopter_libs.a(SIM_Aircraft.cpp.4.o):SIM_Aircraft.cpp:(.text$_ZN4SITL8Aircraft15sync_frame_timeEv+0x152): undefined reference to `_imp__timeGetTime@0'
ArduCopter/libArduCopter_libs.a(SIM_Aircraft.cpp.4.o):SIM_Aircraft.cpp:(.text$_ZNK4SITL8Aircraft16get_wall_time_usEv+0xe): more undefined references to `_imp__timeGetTime@0' follow
collect2: error: ld returned 1 exit status
Since we escape $PATH, we can't just try to export that way. Since PATH
is unset if we do this, we end up with things like :
./Tools/scripts/install-prereqs-ubuntu.sh: line 101: apt-cache: command
not found
If we are running the script, we are likely inside the repository, in
which case the script would fail while searching for a directory named
ardupilot. Derive the root directory from the script location.
ubuntu@ubuntu-xenial:~/ardupilot$ ./Tools/scripts/install-prereqs-ubuntu.sh
./Tools/scripts/install-prereqs-ubuntu.sh: line 19: python-wxgtk3.0: command not found
While at each, change to use lsb_release like the other scripts.
