UCRTVersion not properly set for Visual Studio Community 2017

[dlangBugzillaToGithub]

Bastiaan Veelo (@veelo) reported this on 2017-11-21T14:01:30Z

Transferred from https://issues.dlang.org/show_bug.cgi?id=17999

Description

When Visual Studio Community is the only version present on Windows 10, with the minimal set of options that satisfies the dmd installer (https://wiki.dlang.org/File:Visual_Studio_Installer.png) then dmd -m64 will fail to link:
LINK : fatal error LNK1104: cannot open file 'libucrt.lib'
Error: linker exited with status 1104

The problem goes away after changing UCRTVersion in C:\D\dmd2\windows\bin\sc.ini:

;UCRTVersion=winv6.3
UCRTVersion=10.0.10240.0


(Fresh dmd install.)