Revert "[Clang] Interpreter test should not depend on system header (#119903)"

This reverts commit 8ab6912.

Author: dcci

clang/test/Interpreter/Inputs/vector

@@ -5,7 +5,7 @@
 //
 // RUN: split-file %s %t
 //
-// RUN: %clang++ -Xclang -nostdsysteminc -I%S/Inputs/ -std=c++20 -fPIC -c %t/vec.cpp -o %t/vec.o
+// RUN: %clang++ -std=c++20 -fPIC -c %t/vec.cpp -o %t/vec.o
 // RUN: %clang++ -shared %t/vec.o -o %t/vec.so
 //
 // RUN: cat %t/Test.cpp | LD_LIBRARY_PATH=%t:$LD_LIBRARY_PATH clang-repl