Mark branch_mul as failing

IREE compiler changes the generated dispatches so the input/output of
the tests no longer apply (we test the intermediate dispatch). Disable
the test for now to see if we want to test the full mlir layer (with
known fixed input/output) or do we want to update the input/output.

Bug: 294402411
Change-Id: I0024973afcdc61a1b9953d8a6bdac1c2c3b874d9

samples/branch_mul/branch_mul.run

diff --git a/samples/branch_mul/branch_mul.run b/samples/branch_mul/branch_mul.run
index 5f8c701..198809c 100644
--- a/samples/branch_mul/branch_mul.run
+++ b/samples/branch_mul/branch_mul.run
@@ -1 +1,3 @@
+// TODO(b/294402411): Fix the test
+// XFAIL: *
 // RUN: ${TEST_RUNNER_CMD} %S/branch_mul_emitc_static