Add back test for r299152

I am hoping the bot failures are addressed by using cc1 for the ThinLTO
backend invocations as well.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@299217 91177308-0d34-0410-b5e6-96231b3b80d8

Author: teresajohnson

test/CodeGen/function-sections.c

@@ -9,6 +9,12 @@
 // RUN: %clang_cc1 -triple x86_64-pc-linux-gnu -S -fdata-sections -o - < %s | FileCheck %s --check-prefix=DATA_SECT
 // RUN: %clang_cc1 -triple x86_64-pc-linux-gnu -S -fno-data-sections -fdata-sections -o - < %s | FileCheck %s --check-prefix=DATA_SECT
 
+// Try again through a clang invocation of the ThinLTO backend.
+// RUN: %clang_cc1 -triple x86_64-pc-linux-gnu -O2 %s -flto=thin -emit-llvm-bc -o %t.o
+// RUN: llvm-lto -thinlto -o %t %t.o
+// RUN: %clang_cc1 -triple x86_64-pc-linux-gnu -O2 -x ir %t.o -fthinlto-index=%t.thinlto.bc -S -ffunction-sections -o - | FileCheck %s --check-prefix=FUNC_SECT
+// RUN: %clang_cc1 -triple x86_64-pc-linux-gnu -O2 -x ir %t.o -fthinlto-index=%t.thinlto.bc -S -fdata-sections -o - | FileCheck %s --check-prefix=DATA_SECT
+
 const int hello = 123;
 void world() {}