* switch to chronos metrics, remove insecure
See https://github.com/status-im/nimbus-eth2/pull/2468
also fixes pcre linking for real, and adds some random build flags that
help nimbus-eth2 stay afloat
* fix help
* don't omit frame pointers on windows
* bump vendor/nimbus-build-system
- add the Nim compiler header to the Nimbus header
- also support the USE_LIBBACKTRACE env var
* "go-checks" target no longer available
Jacek Sieka
Ștefan Talpalaru