[lit] Add support for attach arbitrary metrics to test results.

- This is a work-in-progress and all details are subject to change, but I am
   trying to build up support for allowing lit to be used as a driver for
   performance tests (or other tests which might want to record information
   beyond simple PASS/FAIL).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190535 91177308-0d34-0410-b5e6-96231b3b80d8

utils/lit/tests/test-data.py

@@ -0,0 +1,12 @@
+# Test features related to formats which support reporting additional test data.
+
+# RUN: %{lit} -j 1 -v %{inputs}/test-data > %t.out
+# RUN: FileCheck < %t.out %s
+
+# CHECK: -- Testing:
+
+# CHECK: PASS: test-data :: metrics.ini
+# CHECK-NEXT: *** TEST 'test-data :: metrics.ini' RESULTS ***
+# CHECK-NEXT: value0: 1
+# CHECK-NEXT: value1: 2.3456
+# CHECK-NEXT: ***