CI: fix broken build of examples
CI: fix broken build of examples

The "pushd; command; popd" pipeline doesn't fail if command exits non-zero.
This has obfuscated that generating the examples has failed due to missing
clang-11 on CI.

Also merge the Build and Lint job, since the set up time for each job
is non-trivial.

cilium/ebpf,cilium/ebpf