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.
Andrew Tridgell
Lucas De Marchi
Andre Kjellstrup
Michael du Breuil
Francisco Ferreira