[flang] add missing header include after 156661 (#157431)

There is a missing header dependency in #156661.

https://lab.llvm.org/buildbot/#/builders/207/builds/6634

Author: jeanPerier

flang/lib/Lower/ConvertCall.cpp

@@ -17,6 +17,7 @@
 #include "flang/Lower/ConvertVariable.h"
 #include "flang/Lower/CustomIntrinsicCall.h"
 #include "flang/Lower/HlfirIntrinsics.h"
+#include "flang/Lower/PFTBuilder.h"
 #include "flang/Lower/StatementContext.h"
 #include "flang/Lower/SymbolMap.h"
 #include "flang/Optimizer/Builder/BoxValue.h"