fa91bf2559 ci: Skip git install if it is already installed (MarcoFalke)
c65fde4831 ci: vary /tmp/env (Sjors Provoost)
Pull request description:
* Currently, running separate CI tasks at the same time may intermittently fail, because they race to read/write `/tmp/env`. Fix this by adding `$CONTAINER_NAME` to the file name.
* Also, add `$USER`, while touching the line, to allow different users to run the same CI task at the same time.
* Also, skip the git install if there is no need.
Ref: https://github.com/bitcoin/bitcoin/pull/29274
ACKs for top commit:
Sjors:
ACK fa91bf2559
BrandonOdiwuor:
ACK fa91bf2559
hebasto:
ACK fa91bf2559.
Tree-SHA512: 9a8479255a2afb6618f9d0796488d9430ba95266b90ce39536a9817c1974ca4049beeaab5355a38b25171f76fc386dbec06b1919aaa079f08a5a0c0a146232c8
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