base: Add unit test for debug.hh

Add unit tests for the functions and classes in debug.hh.

breakpoint() is not being tested.

Change-Id: I1ae7318a043aa9dc479d4f970c1fd6c9946f4357
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/38710
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/base/debug.cc

@@ -94,8 +94,7 @@ Flag::Flag(const char *name, const char *desc)
     std::pair<FlagsMap::iterator, bool> result =
         allFlags().insert(std::make_pair(name, this));
 
-    if (!result.second)
-        panic("Flag %s already defined!", name);
+    panic_if(!result.second, "Flag %s already defined!", name);
 
     ++allFlagsVersion;