Dont mangle when targeting cpp (#23335)

Unfortunately we cant trick the debugger when targeting C++ so this one
also needs to wait for our own debugger adapter.

(cherry picked from commit 90fe1b340f)

compiler/ccgtypes.nim

@@ -70,7 +70,7 @@ proc mangleProc(m: BModule; s: PSym; makeUnique: bool): string =
 proc fillBackendName(m: BModule; s: PSym) =
   if s.loc.r == "":
     var result: Rope
-    if s.kind in routineKinds and optCDebug in m.g.config.globalOptions and
+    if not m.compileToCpp and s.kind in routineKinds and optCDebug in m.g.config.globalOptions and
       m.g.config.symbolFiles == disabledSf: 
       result = mangleProc(m, s, false).rope
     else:

tests/codegen/titaniummangle.nim

@@ -1,5 +1,5 @@
 discard """
-  targets: "c cpp"
+  targets: "c"
   matrix: "--debugger:native"
   ccodecheck: "'_ZN14titaniummangle8testFuncE'"
   ccodecheck: "'_ZN14titaniummangle8testFuncE6stringN14titaniummangle3FooE'"