[Driver] Always fall back to an arclite in the Xcode default toolchain (#22911)
...instead of the current toolchain, which we would have just
searched by looking relative to the swiftc binary.
rdar://problem/48044350
diff --git a/lib/Driver/DarwinToolChains.cpp b/lib/Driver/DarwinToolChains.cpp
index 0ece134..1e26ab8 100644
--- a/lib/Driver/DarwinToolChains.cpp
+++ b/lib/Driver/DarwinToolChains.cpp
@@ -169,7 +169,9 @@
auto xcrunPath = llvm::sys::findProgramByName("xcrun");
if (!xcrunPath.getError()) {
- const char *args[] = {"-f", "clang", nullptr};
+ // Explicitly ask for the default toolchain so that we don't find a Clang
+ // included with an open-source toolchain.
+ const char *args[] = {"-toolchain", "default", "-f", "clang", nullptr};
sys::TaskQueue queue;
queue.addTask(xcrunPath->c_str(), args, /*Env=*/llvm::None,
/*Context=*/nullptr,