Windows: add windows_testing.bashrc

Lets us pass the `--strip-trailing-cr` option to `diff` on Windows
without changing the Unix tests.

tests/windows_testing.bashrc

@@ -0,0 +1,11 @@
+# bashrc to be used for running tests on windows.
+# In order for the functions to be usable by the tests, we need to use the -i option.
+# Typical usage:
+#   bash --rcfile windows_testing.bashrc -ci "some/test/script.sh"
+
+# During testing we diff Windows files with Unix files => need to ignore the carriage
+# return.
+function diff {
+    command diff --strip-trailing-cr "$@"
+}
+export -f diff