docs(profile): panic behavior can be specified for custom harness

Author: weihanglo

src/doc/src/reference/profiles.md

@@ -208,6 +208,10 @@ The `rustc` test harness currently requires `unwind` behavior. See the
 Additionally, when using the `abort` strategy and building a test, all of the
 dependencies will also be forced to build with the `unwind` strategy.
 
+One exception is that when a test or benchmark target is driven by a custom
+harness, panic setting will be applied since the custom harness may not have
+the same limitation as the `rustc` test harness requires.
+
 [`-C panic` flag]: ../../rustc/codegen-options/index.html#panic
 [`panic-abort-tests`]: unstable.md#panic-abort-tests