Add windows-nt build specifics

[lispstudent]

See #2828

[lispstudent]

Successful install after proposed commit,

el-get install bbdb
el-get: Package bbdb installed.
el-get: git submodule update ok
el-get: el-get-build bbdb: sh autogen.sh ok.
el-get: el-get-build bbdb: sh configure ok.
el-get: el-get-build bbdb: make ok.
el-get is waiting for "c:/msys64/usr/bin/install-info.exe" to complete
el-get: el-get-build bbdb: c:/msys64/usr/bin/install-info.exe c:/home/.emacs.d/el-get/bbdb/doc/bbdb.info dir ok.
el-get is waiting for "byte-compile" to complete
el-get: el-get-build bbdb: byte-compile ok. [2 times]
bbdb installed: This package has been installed successfully by el-get.