mobile: Make C++17 a default build target

[fredyw]

This is so that when building it locally, it will also use C++17 without having to manually pass --cxxopt=-std=c++17 --host_cxxopt=-std=c++17.

Risk Level: low Testing: CI Docs Changes: n/a Release Notes: n/a Platform Specific Features: n/a

[repokitteh-read-only[bot]]

As a reminder, PRs marked as draft will not be automatically assigned reviewers, or be handled by maintainer-oncall triage.

Please mark your PR as ready when you want it to be reviewed!

:cat:

Caused by: https://github.com/envoyproxy/envoy/pull/34209 was opened by fredyw.

see: more, trace.

[phlax]

fwiw im just about to test the newer ndk https://github.com/envoyproxy/envoy-build-tools/commit/6474ce1eddb779bd0fd1ca3a60995687fbf00bb4

[fredyw]

/retest

[fredyw]

/retest

[fredyw]

/retest

[fredyw]

/assign @abeyad