If you have a VM host like parallels, sometimes you get these link-local
default routes:
```
netstat -nrfinet | grep "default\|\/1"
0/1 10.2.0.12 UGScg feth4823
default 192.168.82.1 UGScg en1
0/1 192.168.82.1 UGScIg en1
default link#22 UCSIg bridge101 !
128.0/1 10.2.0.12 UGSc feth4823
128.0/1 192.168.82.1 UGScI en1
```
(the link#22 one)
The _getRTEs function inclused these routes in the list it makes as like:
device: bridge101, target: 0.0.0.0/0
If it happens to be first in the list, bridge101 gets
selected as the default route.
Then Full Tunnel Mode doesn't work.
The other routes in the list are like:
device: en1 target: 192.168.1.0/24 via: metric: 0 ifscope: 0
device: en1 target: 192.168.1.1/32 via: metric: 0 ifscope: 0
We only need the device name from this, so either one will work.
Through using ndk-build, -Wno-unused-command-line-argument is passed in
somewhere in the pipeline and hides this warning.
The warning can be turned on with:
APP_CPPFLAGS := -Wunused-command-line-argument ...
and then when building, you can see:
C/C++: clang++: warning: argument unused during compilation: '-mfloat-abi=softfp' [-Wunused-command-line-argument]
C/C++: clang++: warning: argument unused during compilation: '-mfpu=neon' [-Wunused-command-line-argument]
C/C++: clang++: warning: argument unused during compilation: '-maes' [-Wunused-command-line-argument]
These are unused because both floating-point and NEON are required in
all standard ARMv8 implementations. [1] [2]
[1] https://developer.arm.com/documentation/den0024/a/AArch64-Floating-point-and-NEON
[2] https://stackoverflow.com/a/29891469
Since NDKr15 (released 2017), unified headers are used by default [1]
Remove -isystem option that was passing bad values to command-line.
The actual value being passed to command-line was:
```
-isystem DK/sysroot/usr/include/RIPLE
```
because of using $NDK and $TRIPLE instead of $(NDK) and $(TRIPLE)
But regardless, $NDK and $TRIPLE were never actually defined values and were just
place-holders mentioned in [1]
[1] https://android.googlesource.com/platform/ndk/+/ndk-release-r16/docs/UnifiedHeaders.md
