Reland "[NFC] Add a missing test for for clang-repl"

[junaire]

Summary

This reverts 3668d1264e2d246f7e222338b8a5cab18ce1bdab
As far as we know, __attribute__((weak)) support has been really bad
in runtimeldyld, so we just disable it in Windows at this moment. This
should fix the angry Windows buildbot.

[v.g.vassilev]

Let's move forward and we can remove the XFAIL once https://reviews.llvm.org/D128968 lands.

clang/test/Interpreter/execute.cpp

 // RUN: clang-repl "int x = 10;" "int y=7; err;" "int y = 10;"
 // RUN: clang-repl "int i = 10;" 'extern "C" int printf(const char*,...);' \
 // RUN:            'auto r1 = printf("i = %d\n", i);' | FileCheck --check-prefix=CHECK-DRIVER %s
 // REQUIRES: host-supports-jit
 // UNSUPPORTED: system-aix
+// XFAIL: windows-msvc
 // CHECK-DRIVER: i = 10
 // RUN: cat %s | clang-repl | FileCheck %s
 extern "C" int printf(const char *, ...);
 int i = 42;
 auto r1 = printf("i = %d\n", i);
 // CHECK: i = 42
 
 struct S { float f = 1.0; S *m = nullptr;} s;
 
 auto r2 = printf("S[f=%f, m=0x%llx]\n", s.f, reinterpret_cast<unsigned long long>(s.m));
 // CHECK-NEXT: S[f=1.000000, m=0x0]
 
 inline int foo() { return 42; }
 int r3 = foo();
 
+int __attribute__((weak)) bar() { return 1; }
+auto r4 = printf("bar() = %d\n", bar());
+// CHECK-NEXT: bar() = 1
+
 %quit