Fix the build with VC++ and dmake (rather than nmake) on Windows. The Makefile generated by Apache2::Build uses shell commands for the manifest file, but neglected to tell dmake to use the shell.

git-svn-id: https://svn.apache.org/repos/asf/perl/modperl/trunk@1477995 13f79535-47bb-0310-9956-ffa450edef68