[clang] [Haiku] Don't assume clang was build with libstdc++ as default (PR #65871)

[via cfe-commits]

llvmbot wrote:

@llvm/pr-subscribers-clang

<details>
<summary>Changes</summary>

This test fails with `CLANG_DEFAULT_CXX_STDLIB=libc++`
--
Full diff: https://github.com/llvm/llvm-project/pull/65871.diff

1 Files Affected:

- (modified) clang/test/Driver/haiku.cpp (+1-1) 


<pre>
diff --git a/clang/test/Driver/haiku.cpp b/clang/test/Driver/haiku.cpp
index f022013d1ef79b..64018e8236b282 100644
--- a/clang/test/Driver/haiku.cpp
+++ b/clang/test/Driver/haiku.cpp
@@ -1,5 +1,5 @@
 // Check the C++ header path (libstdc++)
-// RUN: %clangxx --target=x86_64-unknown-haiku -### %s 2>&1 \
+// RUN: %clangxx --target=x86_64-unknown-haiku --stdlib=libstdc++ -### %s 2>&1 \
 // RUN:   --sysroot=%S/Inputs/haiku_x86_64_tree \
 // RUN:   | FileCheck --check-prefix=CHECK-LIBSTDCXX-HEADER-PATH %s
 // CHECK-LIBSTDCXX-HEADER-PATH: "-internal-isystem" "[[SYSROOT:[^"]+]]/boot/system/develop/headers/c++"
</pre>

</details>

https://github.com/llvm/llvm-project/pull/65871