Getting most of the tests running on Windows.

This adds proper iree_cc_test and iree_lit_test execution via cmake test on Windows. A handful of tests are failing due to file IO issues that will be fixed in follow-on changes.

Closes https://github.com/google/iree/pull/899

COPYBARA_INTEGRATE_REVIEW=https://github.com/google/iree/pull/899 from google:benvanik-win32-test 1ef44695c721f0edc82e49aec3737e18356bbbe8
PiperOrigin-RevId: 298599246
diff --git a/build_tools/cmake/iree_macros.cmake b/build_tools/cmake/iree_macros.cmake
index 4afc54e..683460a 100644
--- a/build_tools/cmake/iree_macros.cmake
+++ b/build_tools/cmake/iree_macros.cmake
@@ -15,6 +15,16 @@
 include(CMakeParseArguments)
 
 #-------------------------------------------------------------------------------
+# Missing CMake Variables
+#-------------------------------------------------------------------------------
+
+if(${CMAKE_HOST_SYSTEM_NAME} STREQUAL "Windows")
+  set(IREE_HOST_SCRIPT_EXT "bat")
+else()
+  set(IREE_HOST_SCRIPT_EXT "sh")
+endif()
+
+#-------------------------------------------------------------------------------
 # Packages and Paths
 #-------------------------------------------------------------------------------