tests: prefer __has_feature(capabilities) to defined(__CHERI__)

Author: brooksdavis

clang/test/CodeGen/builtin-align.c

@@ -40,7 +40,7 @@
 #error MISSING TYPE
 #endif
 
-#ifndef __CHERI__
+#if !__has_feature(capabilities)
 #define __capability
 #endif
 

clang/test/SemaCXX/cheri/cheri-pointer-cast.cpp

@@ -9,7 +9,7 @@ typedef unsigned long ulong;
 
 int foo;
 
-#ifdef __CHERI__
+#if __has_feature(capabilities)
 #define CAP __capability
 #else
 #define CAP
@@ -68,7 +68,7 @@ int main() {
 }
 
 // Check that we don't warn on dependent types
-#ifdef __CHERI__
+#if __has_feature(capabilities)
 template <typename T>
 long offset_get(T x) {
   return __builtin_cheri_offset_get(reinterpret_cast<void * __capability>(x));