[llvm] [BOLT][merge-fdata] Fix basic sample profile aggregation without LBR info (PR #118481)

[Paschalis Mpeis via llvm-commits]

================
@@ -0,0 +1,7 @@
+## Check that merge-fdata tool correctly reports error message
+## when trying to merge 'no-lbr' and 'lbr' profiles
+# RUN: not merge-fdata %S/Inputs/no-lbr_profile_1.fdata \
+# RUN:                      %S/Inputs/lbr_profile.fdata \
+# RUN:                                     | FileCheck %s
----------------
paschalis-mpeis wrote:

This test is failing. Probably you forgot to redirect stderr to stdout before piping to `FileCheck`

https://github.com/llvm/llvm-project/pull/118481