tdf#108580: integrate vc_redist.exe into Windows installer

[Mike Kaganski]

Hi!

Some time ago, we had a ESC decision [1] to use a workaround for bug 
108580 [2] about problem with VCRedist, which stopped to install 
essential part of libraries on Windows Vista and above (currently 
affected are Win7, Win8, and Win8.1), which was done in 
71d9a61302e65fe091cf70c13fa72b3df09b7e3a [3], and "for 6.0 do something 
clever".

Here is the proposal [4] that pretends to be clever :)
The following is essentially a copy-paste from the patch commit message:

Since commit 71d9a61302e65fe091cf70c13fa72b3df09b7e3a, we use a 
workaround described at [5] as "App-local deployment of the Universal 
CRT". We just copy all UCRT DLLs to LibreOffice/program. This has a 
drawback though, that our UCRT is not updated by Windows Update, so 
users would rely on LibreOffice updates in case of some vulnerabilities 
in UCRT (and they could even not realize they have that problem).

MS recommends to install UCRT using EXEs they provide from their site. 
The EXEs install both VCRuntimes and UCRTs, along with required patches, 
for all Windows versions (Windows XP through Windows 10, where they only 
install VCRuntimes); the installed libraries are managed by system's 
update mechanism. But those EXEs cannot be used in MSI custom actions 
inside InstallExecuteSequence, because they use MSI themselves.

So this patch integrates the vc_redist.xXX.exe into MSI binary table, 
and uses custom action to run the EXE after ExecuteAction in 
InstallUISequence. This will show the user a VCRedist install window 
after the main LibreOffice installation finishes; no user interaction is 
required (except one more UAC request), and errors are ignored.

Since this installation takes care of both VCRuntime and UCRT, we can 
ultimately drop both the app-local workaround, and vcredist merge module 
(so VCRuntime would also be updated by system).

This has its drawback: if one wants to use unattended installation 
(without UI; one example is deployment using ActiveDirectory GPO), then 
InstallUISequence is not run, and so VCRedist isn't installed. In this 
case, one should install VCRedist separately. Supposedly this should not 
be huge problem, because this is the case for many existing applications 
that need separate VCRedist deployment in these scenarios.

Please share your opinions. Is this change viable?

The patch itself IMO needs some polish: I suppose that we should remove 
redundant workaround (and possibly even merge module bits) if we accept 
it. But it is in working state, so testing is possible.

[1] 
https://lists.freedesktop.org/archives/libreoffice-qa/2017-November/010300.html
[2] https://bugs.documentfoundation.org/show_bug.cgi?id=108580
[3] 
https://cgit.freedesktop.org/libreoffice/core/commit/?id=71d9a61302e65fe091cf70c13fa72b3df09b7e3a
[4] https://gerrit.libreoffice.org/46356
[5] 
https://blogs.msdn.microsoft.com/vcblog/2015/03/03/introducing-the-universal-crt/

-- 
Best regards,
Mike Kaganski