CI updates.

* js/azure-pipelines-msvc:
  ci: also build and test with MS Visual Studio on Azure Pipelines
  ci: really use shallow clones on Azure Pipelines
  tests: let --immediate and --write-junit-xml play well together
  test-tool run-command: learn to run (parts of) the testsuite
  vcxproj: include more generated files
  vcxproj: only copy `git-remote-http.exe` once it was built
  msvc: work around a bug in GetEnvironmentVariable()
  msvc: handle DEVELOPER=1
  msvc: ignore some libraries when linking
  compat/win32/path-utils.h: add #include guards
  winansi: use FLEX_ARRAY to avoid compiler warning
  msvc: avoid using minus operator on unsigned types
  push: do not pretend to return `int` from `die_push_simple()`