XFAIL thinlto testcases on AIX

In D100350, we switched off thinLTO on the AIX OS. So, XFAIL tests that
invoke clang with -flto=thin on AIX.

clang/test/CodeGen/thinlto-backend-option.ll

@@ -6,6 +6,8 @@
 ; scenario independent of any particular backend options that may exist now or
 ; in the future.
 
+; XFAIL: aix
+
 ; RUN: %clang -flto=thin -c -o %t.o %s
 ; RUN: llvm-lto -thinlto -o %t %t.o
 ; RUN: not %clang_cc1 -x ir %t.o -fthinlto-index=%t.thinlto.bc -mllvm -nonexistent -emit-obj -o /dev/null 2>&1 | FileCheck %s -check-prefix=UNKNOWN

clang/test/CodeGen/thinlto-emit-llvm.c

@@ -1,3 +1,5 @@
+// XFAIL: aix
+
 // Test to ensure -emit-llvm and -emit-llvm-bc work when invoking the
 // ThinLTO backend path.
 // RUN: %clang -O2 %s -flto=thin -c -o %t.o

clang/test/Driver/thinlto_backend.c

@@ -1,3 +1,5 @@
+// XFAIL: aix
+
 // RUN: %clang -O2 %s -flto=thin -c -o %t.o
 // RUN: llvm-lto -thinlto -o %t %t.o
 

clang/test/Integration/thinlto_profile_sample_accurate.c

@@ -1,3 +1,5 @@
+// XFAIL: aix
+
 // Test to ensure -emit-llvm profile-sample-accurate is honored in ThinLTO.
 // RUN: %clang -O2 %s -flto=thin -fprofile-sample-accurate -c -o %t.o
 // RUN: llvm-lto -thinlto -o %t %t.o