Merge branch 'hotfix/1.19.3' into stable
Fix sending wrong argument --add-to-rvm-group to scripts/install

This is already set via environment variable, and was not being sent correctly
to scripts/install, causing problems when using it.
Merge pull request #1794 from OSSystems/master

Fix: binscripts/rvm-installer is sending malformed arguments to scripts/install when using the --add-to-rvm-group on multiuser environments
Allow git-core if git is missing.
For 1.19.2
Check for preinstalled packages. Fixes #1795.
NEXT: [GH-1795] for 1.19.4
1.19.4
Allow git-core if git is missing.
Conflicts:
	scripts/functions/requirements/ubuntu
Check for preinstalled packages. Fixes #1795.
Merge branch 'hotfix/1.19.4'

Conflicts:
	scripts/functions/requirements/ubuntu
NEXT: 1.19.4 ready