[Driver] Fuchsia targets default to -fasynchronous-unwind-tables

[mcgrathr]

Summary

This regressed for x86-64 in r307856 because it's no longer inherited
from Generic_GCC. We'd never noticed that it was missing other
targets (i.e. aarch64), but Fuchsia is uniform across all machines.

[phosek]

LGTM

lib/Driver/ToolChains/Fuchsia.h

public:
   bool IsIntegratedAssemblerDefault() const override { return true; }
   bool IsMathErrnoDefault() const override { return false; }
   RuntimeLibType GetDefaultRuntimeLibType() const override {
     return ToolChain::RLT_CompilerRT;
   }
   CXXStdlibType GetDefaultCXXStdlibType() const override {
     return ToolChain::CST_Libcxx;
   }
+  bool IsUnwindTablesDefault(const llvm::opt::ArgList &Args) const override {
+    return true;
+  }
   bool isPICDefault() const override { return false; }
   bool isPIEDefault() const override { return true; }
   bool isPICDefaultForced() const override { return false; }
   llvm::DebuggerKind getDefaultDebuggerTuning() const override {
     return llvm::DebuggerKind::GDB;
   }
 
   std::string ComputeEffectiveClangTriple(const llvm::opt::ArgList &Args,

test/Driver/fuchsia.c

 // RUN: %clang %s -### -no-canonical-prefixes --target=x86_64-unknown-fuchsia \
-// RUN:     --sysroot=%S/platform -fuse-ld=ld 2>&1 | FileCheck %s
+// RUN:     --sysroot=%S/platform -fuse-ld=ld 2>&1 \
+// RUN:     | FileCheck -check-prefixes=CHECK,CHECK-X86_64 %s
+// RUN: %clang %s -### -no-canonical-prefixes --target=aarch64-unknown-fuchsia \
+// RUN:     --sysroot=%S/platform -fuse-ld=ld 2>&1 \
+// RUN:     | FileCheck -check-prefixes=CHECK,CHECK-AARCH64 %s
 // CHECK: {{.*}}clang{{.*}}" "-cc1"
+// CHECK: "-munwind-tables"
 // CHECK: "-fuse-init-array"
 // CHECK: "-isysroot" "[[SYSROOT:[^"]+]]"
 // CHECK: "-internal-externc-isystem" "[[SYSROOT]]{{/|\\\\}}include"
 // CHECK: {{.*}}lld{{.*}}" "-flavor" "gnu"
 // CHECK: "-z" "rodynamic"
 // CHECK: "--sysroot=[[SYSROOT]]"
 // CHECK: "-pie"
 // CHECK: "--build-id"
 // CHECK: "--hash-style=gnu"
 // CHECK: "-dynamic-linker" "ld.so.1"
 // CHECK: Scrt1.o
 // CHECK-NOT: crti.o
 // CHECK-NOT: crtbegin.o
 // CHECK: "-L[[SYSROOT]]{{/|\\\\}}lib"
-// CHECK: "{{.*[/\\]}}libclang_rt.builtins-x86_64.a"
+// CHECK-X86_64: "{{.*[/\\]}}libclang_rt.builtins-x86_64.a"
+// CHECK-AARCH64: "{{.*[/\\]}}libclang_rt.builtins-aarch64.a"
 // CHECK: "-lc"
 // CHECK-NOT: crtend.o
 // CHECK-NOT: crtn.o
 
 // RUN: %clang %s -### --target=x86_64-unknown-fuchsia -rtlib=libgcc 2>&1 \
 // RUN:     | FileCheck %s -check-prefix=CHECK-RTLIB
 // CHECK-RTLIB: error: invalid runtime library name in argument '-rtlib=libgcc'