compiler: Ensure __builtin_*_overflow() support

Both gcc and clang support this for a long time.
Make sure the feature is present.

Signed-off-by: Richard Weinberger <richard@nod.at>

include/linux/compiler_types.h

@@ -70,6 +70,13 @@ extern void __chk_io_ptr(const volatile void __iomem *);
 #error "Unknown compiler"
 #endif
 
+/*
+ * At least gcc 5.1 or clang 8 are needed.
+ */
+#ifndef COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW
+#error Unsupported compiler
+#endif
+
 /*
  * Some architectures need to provide custom definitions of macros provided
  * by linux/compiler-*.h, and can do so using asm/compiler.h. We include that