test: add a local lit configuration for Interop

This adds a local lit configuration for simplifying matching against
different ABIs.

Author: compnerd

test/Interop/lit.local.cfg

@@ -0,0 +1,14 @@
+# Make a local copy of the substitutions.
+config.substitutions = list(config.substitutions)
+
+def get_target_os():
+    import re
+    (run_cpu, run_vendor, run_os, run_version) = re.match('([^-]+)-([^-]+)-([^0-9]+)(.*)', config.variant_triple).groups()
+    return run_os
+
+if get_target_os() in ['windows-msvc']:
+    config.substitutions.insert(0, ('%target-abi', 'WIN'))
+else:
+    # FIXME(compnerd) do all the targets we currently support use SysV ABI?
+    config.substitutions.insert(0, ('%target-abi', 'SYSV'))
+