L4: enable GCC 12

diff --git a/l4/mk/Makeconf b/l4/mk/Makeconf
index eb59b51..a7b5955 100644
--- a/l4/mk/Makeconf
+++ b/l4/mk/Makeconf
@@ -52,7 +52,7 @@ L4_KIP_OFFS_SYS_DEBUGGER = 0x900
 L4_STACK_ADDR           ?= $(L4_STACK_ADDR_$(ARCH))
 L4_STACK_SIZE           ?= $(if $(L4_STACK_SIZE_MAIN_THREAD),$(L4_STACK_SIZE_MAIN_THREAD),0x8000)
 
-CC_WHITELIST-gcc     := 4.7 4.8 4.9 5 6 7 8 9
+CC_WHITELIST-gcc     := 4.7 4.8 4.9 5 6 7 8 9 10 11 12
 CC_WHITELIST-clang   := 3.5 3.6 3.7 3.8 3.9
 
 # This is quite bad: There is no other chance to disable the page-alignedment