[cxx-interop] Do not crash for static operator()

This fixes an assertion failure:
```
Assertion failed: (isInstance() && "No 'this' for static methods!"), function getThisType, file DeclCXX.cpp, line 2636.
```

Clang changed it's handling of member call expressions in llvm/llvm-project@af47517 causing the assertion to fail when synthesizing a forwarding function declaration for `static operator()`.

rdar://133257179

Author: egorzhdan

lib/ClangImporter/SwiftDeclSynthesizer.cpp

@@ -2149,14 +2149,19 @@ clang::CXXMethodDecl *SwiftDeclSynthesizer::synthesizeCXXForwardingMethod(
     thisExpr = conv.get();
   }
 
+  auto memberExprTy =
+      (method->isStatic() && method->getOverloadedOperator() ==
+                                 clang::OverloadedOperatorKind::OO_Call)
+          ? method->getType()
+          : clangCtx.BoundMemberTy;
   auto memberExpr = clangSema.BuildMemberExpr(
       thisExpr, /*isArrow=*/true, clang::SourceLocation(),
       clang::NestedNameSpecifierLoc(), clang::SourceLocation(),
       const_cast<clang::CXXMethodDecl *>(method),
       clang::DeclAccessPair::make(const_cast<clang::CXXMethodDecl *>(method),
                                   clang::AS_public),
       /*HadMultipleCandidates=*/false, method->getNameInfo(),
-      clangCtx.BoundMemberTy, clang::VK_PRValue, clang::OK_Ordinary);
+      memberExprTy, clang::VK_PRValue, clang::OK_Ordinary);
   llvm::SmallVector<clang::Expr *, 4> args;
   for (size_t i = 0; i < newMethod->getNumParams(); ++i) {
     auto *param = newMethod->getParamDecl(i);
@@ -2167,7 +2172,7 @@ clang::CXXMethodDecl *SwiftDeclSynthesizer::synthesizeCXXForwardingMethod(
         clangCtx, param, false, type, clang::ExprValueKind::VK_LValue,
         clang::SourceLocation()));
   }
-  auto memberCall = clangSema.BuildCallToMemberFunction(
+  auto memberCall = clangSema.BuildCallExpr(
       nullptr, memberExpr, clang::SourceLocation(), args,
       clang::SourceLocation());
   if (!memberCall.isUsable())