Revert "Avoid msbuild idiosyncrasy that builds multiple configs" (#11633)

This reverts commit 57e71533f4.

While "msbuild" can handle full paths to project files in solutions,
the old "vcbuild" used for VS < 10 cannot.  We will need another
way to fix issue #11594.

Source/cmGlobalVisualStudio7Generator.cxx

@@ -297,6 +297,8 @@ void cmGlobalVisualStudio7Generator::WriteTargetsToSolution(
         {
         cmMakefile* tmf = target->GetMakefile();
         std::string dir = tmf->GetStartOutputDirectory();
+        dir = root->Convert(dir.c_str(),
+                            cmLocalGenerator::START_OUTPUT);
         this->WriteProject(fout, vcprojName, dir.c_str(),
                            *target);
         written = true;