I did a clean install of windows 10 and visual studio 2015 and did not find makecert.exe anywhere. Does some other software need to be installed to get this program back?
A quick search of my C: found that makecert.exe seems to be distributed with Fiddler 2 in the C:\Program Files (x86)\Fiddler2 folder. This is a much smaller download than the full Windows SDK.
For the record I have version 4.6.20171.26113 of Fiddler 2.