Create strict aligned code for OpenBSD/arm64.

(cherry picked from commit 44613bb)

Author: brad0

clang/lib/Driver/ToolChains/Arch/AArch64.cpp

@@ -370,9 +370,11 @@ void aarch64::getAArch64TargetFeatures(const Driver &D,
     V8_6Pos = Features.insert(std::next(V8_6Pos), {"+i8mm", "+bf16"});
 
   if (Arg *A = Args.getLastArg(options::OPT_mno_unaligned_access,
-                               options::OPT_munaligned_access))
+                               options::OPT_munaligned_access)) {
     if (A->getOption().matches(options::OPT_mno_unaligned_access))
       Features.push_back("+strict-align");
+  } else if (Triple.isOSOpenBSD())
+    Features.push_back("+strict-align");
 
   if (Args.hasArg(options::OPT_ffixed_x1))
     Features.push_back("+reserve-x1");

clang/test/Driver/arm-alignment.c

@@ -80,6 +80,9 @@
 // RUN: %clang -target aarch64-none-gnueabi -mkernel -mno-unaligned-access -### %s 2> %t
 // RUN: FileCheck --check-prefix=CHECK-ALIGNED-AARCH64 < %t %s
 
+// RUN: %clang -target aarch64-unknown-openbsd -### %s 2> %t
+// RUN: FileCheck --check-prefix=CHECK-ALIGNED-AARCH64 < %t %s
+
 // CHECK-ALIGNED-ARM: "-target-feature" "+strict-align"
 // CHECK-ALIGNED-AARCH64: "-target-feature" "+strict-align"