build failures with linux_amd64_debian9
In case of libosmocore (current master), the default master build job is using linux_amd64_debian8 build host where everything works fine. If we enable newer linux_amd64_debian9 than we hit build failures.
Possible reason is that the newer toolchain in Debian9 is strickter than the one used in Debian 8.
We should migrate all the builds to linux_amd64_debian9 to make sure we catch as many errors as possible.
It's been reported as well that AddressSanitizer is more strict in Debian 9 too which should improve code quality as well.
The migration should probably happen on project-by-project basis to distinguish between issues uncovered in dependencies from issues found in the project itself.
An example of such an issue and fix: https://gerrit.osmocom.org/#/c/5159/