Enable -Wtrampolines by default.

--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -640,7 +640,7 @@ Common Var(warn_system_headers) Warning
 Do not suppress warnings from system headers
 
 Wtrampolines
-Common Var(warn_trampolines) Warning
+Common Var(warn_trampolines) Init(1) Warning
 Warn whenever a trampoline is generated
 
 Wtype-limits
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -4007,6 +4007,8 @@ headers---for that, @option{-Wunknown-pragmas} must also be used.
  for most targets, it is made up of code and thus requires the stack
  to be made executable in order for the program to work properly.
 
+ This warning is enabled by default in Gentoo.
+
 @item -Wfloat-equal
 @opindex Wfloat-equal
 @opindex Wno-float-equal
