libc++1 is kept back after upgrade to new ubuntu release

[Karol]

The upgrade process went very smooth with it asking me to approve some fixes to a few files I have modified on my own. After the upgrade I run:
`sudo apt update && sudo apt upgrade`.

I expected this to show no updates, or maybe just a few minor ones, but instead I got:
```Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
The following packages have been kept back:
  libc++1
0 upgraded, 0 newly installed, 0 to remove and 1 not upgraded.
```

It's fixed by
`sudo apt install libc++1`
but should be considered a bug in the upgrade process.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: ubuntu-release-upgrader-core 1:20.04.18
ProcVersionSignature: Ubuntu 5.4.0-28.32-generic 5.4.30
Uname: Linux 5.4.0-28-generic x86_64
ApportVersion: 2.20.11-0ubuntu27
Architecture: amd64
CasperMD5CheckResult: skip
CrashDB: ubuntu
CurrentDesktop: ubuntu:GNOME
Date: Fri May 1 13:05:36 2020
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
Symptom: dist-upgrade
UpgradeStatus: Upgraded to focal on 2020-05-01 (0 days ago)
VarLogDistupgradeTermlog:

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Øby (stian-oby)]

I had the same issue, and the solution posted here appears to have worked perfectly:
https://ubuntuforums.org/showthread.php?t=2441409

(Make sure to do the simulation with the -s flag first, to ensure that there are no other packages affected by a forced upgrade than those of libc++1* packages – see the example output of the simulation run in the above-linked thread.

[terry b (tbohaning-gmail)]

This issue also exists in 20.10. The fix works as well.

[Max Barry (max-maxbarry)]

Same as comment #4, I encountered this issue after upgrading from 20.04 -> 20.10. So it's not specific to an upgrade to focal.

[terry b (tbohaning-gmail)]

This issue also exists in 21.04 beta. Same solution works. It didn't show up until today.

[Karol (wasowski02)]

I have also experienced it on upgrading to 21.04 beta

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Øby (stian-oby)]

Experienced the same after upgrading to 21.04 (final) today.

"Solved" by using the workaround:
sudo apt-get install libc++1/hirsute

[ali_hamdi (hamdi-ali-1982)]

I had the same issue when upgrading to 21.04. I couldn't solve it by
 sudo apt-get install libc++1/hirsute
But when trying
 sudo apt-get install libc++1
It worked perfectly