[clang] [CIR] Upstream EHScopeStack memory allocator (PR #152215)

[Henrich Lauko via cfe-commits]

================
@@ -33,6 +34,54 @@ using namespace clang::CIRGen;
 
 void EHScopeStack::Cleanup::anchor() {}
 
+/// Push an entry of the given size onto this protected-scope stack.
+char *EHScopeStack::allocate(size_t size) {
+  size = llvm::alignTo(size, ScopeStackAlignment);
+  if (!startOfBuffer) {
+    unsigned capacity = 1024;
+    while (capacity < size)
+      capacity *= 2;
----------------
xlauko wrote:

```suggestion
    unsigned capacity = llvm::PowerOf2Ceil(std::max(size, 1024u));
```

https://github.com/llvm/llvm-project/pull/152215