...
It turns out that the makefile described above is deprecated. (I believe that) The top level makefile can be used on an clean curl source, and an OpenSSL distribution build "nmake imnstallinstall_sw".
The following files dependencies subdirectory of the cpp-msbuild project can be used to automate the build:
config.bat
to set up the environmentlibcurl-new.bat
andlibcurl-new-x64
to compile (requires the appropriate VS command line)