[Exegesis] Fix test failures from #122775 on MacOSX and Fuchsia

I'm making this test to run only when exegesis-can-execute-x86_64.

Author: mshockwave

llvm/test/tools/llvm-exegesis/X86/dry-run-measurement.test

@@ -0,0 +1,10 @@
+# RUN: llvm-exegesis --mode=latency --opcode-name=LEA64r --use-dummy-perf-counters --benchmark-phase=dry-run-measurement | FileCheck %s
+# REQUIRES: exegesis-can-execute-x86_64
+
+# This test makes sure that llvm-exegesis doesn't execute any snippet in the presence of dry-run measurement.
+
+# Should not contain misleading results.
+# CHECK: measurements:    []
+
+# Should not contain any error message.
+# CHECK: error:           ''