[Driver][OpenBSD] Disable unwind tables on Arm

Arm is not quite ready for unwinding yet.

(cherry picked from commit 9abeb80)

Author: brad0

clang/lib/Driver/ToolChains/OpenBSD.cpp

@@ -342,3 +342,12 @@ Tool *OpenBSD::buildAssembler() const {
 Tool *OpenBSD::buildLinker() const { return new tools::openbsd::Linker(*this); }
 
 bool OpenBSD::HasNativeLLVMSupport() const { return true; }
+
+bool OpenBSD::IsUnwindTablesDefault(const ArgList &Args) const {
+    switch (getArch()) {
+      case llvm::Triple::arm:
+        return false;
+      default:
+        return true;
+    }
+}

clang/lib/Driver/ToolChains/OpenBSD.h

@@ -82,9 +82,7 @@ class LLVM_LIBRARY_VISIBILITY OpenBSD : public Generic_ELF {
   std::string getCompilerRT(const llvm::opt::ArgList &Args, StringRef Component,
                             FileType Type = ToolChain::FT_Static) const override;
 
-  bool IsUnwindTablesDefault(const llvm::opt::ArgList &Args) const override {
-    return true;
-  }
+  bool IsUnwindTablesDefault(const llvm::opt::ArgList &Args) const override;
 
   LangOptions::StackProtectorMode
   GetDefaultStackProtectorLevel(bool KernelOrKext) const override {

clang/test/Driver/openbsd.c

@@ -124,7 +124,8 @@
 
 // Check that unwind tables are enabled
 // RUN: %clang -target arm-unknown-openbsd -### -S %s 2>&1 | \
-// RUN: FileCheck -check-prefix=UNWIND-TABLES %s
+// RUN: FileCheck -check-prefix=NO-UNWIND-TABLES %s
 // RUN: %clang -target mips64-unknown-openbsd -### -S %s 2>&1 | \
 // RUN: FileCheck -check-prefix=UNWIND-TABLES %s
 // UNWIND-TABLES: "-funwind-tables=2"
+// NO-UNWIND-TABLES-NOT: "-funwind-tables=2"