Revert r301697 "[IR] Make add/remove Attributes use AttrBuilder instead of AttributeList"

This broke the Clang build. (Clang-side patch missing?)

Original commit message:

> [IR] Make add/remove Attributes use AttrBuilder instead of
> AttributeList
>
> This change cleans up call sites and avoids creating temporary
> AttributeList objects.
>
> NFC

llvm-svn: 301712
diff --git a/llvm/unittests/IR/AttributesTest.cpp b/llvm/unittests/IR/AttributesTest.cpp
index 0df7a84..7c3df2e 100644
--- a/llvm/unittests/IR/AttributesTest.cpp
+++ b/llvm/unittests/IR/AttributesTest.cpp
@@ -45,7 +45,7 @@
                          AttributeList::get(C, 1, Attribute::SExt)};
 
   AttributeList SetA = AttributeList::get(C, ASs);
-  AttributeList SetB = SetA.removeAttributes(C, 1, ASs[1].getAttributes(1));
+  AttributeList SetB = SetA.removeAttributes(C, 1, ASs[1]);
   EXPECT_NE(SetA, SetB);
 }