[Driver] Enable SafeStack for Fuchsia targets

[mcgrathr]

Summary

The runtime support is provided directly by the Fuchsia system C library.

[mcgrathr]

This assumes https://reviews.llvm.org/D30237

[phosek]

Could you also please update test/Driver/fuchsia.c and add a case for -fsanitize=safe-stack?

[mcgrathr]

Added test case.

[phosek]

LGTM

cfe/trunk/lib/Driver/ToolChains.h

public:
 
   bool isPIEDefault() const override { return true; }
   bool HasNativeLLVMSupport() const override { return true; }
   bool IsIntegratedAssemblerDefault() const override { return true; }
   llvm::DebuggerKind getDefaultDebuggerTuning() const override {
     return llvm::DebuggerKind::GDB;
   }
 
+  SanitizerMask getSupportedSanitizers() const override;
+
   RuntimeLibType
   GetRuntimeLibType(const llvm::opt::ArgList &Args) const override;
   CXXStdlibType
   GetCXXStdlibType(const llvm::opt::ArgList &Args) const override;
 
   void addClangTargetOptions(const llvm::opt::ArgList &DriverArgs,
                              llvm::opt::ArgStringList &CC1Args) const override;
   void

cfe/trunk/lib/Driver/ToolChains.cpp

 void Fuchsia::AddCXXStdlibLibArgs(const ArgList &Args,
                                   ArgStringList &CmdArgs) const {
   (void) GetCXXStdlibType(Args);
   CmdArgs.push_back("-lc++");
   CmdArgs.push_back("-lc++abi");
   CmdArgs.push_back("-lunwind");
 }
 
+SanitizerMask Fuchsia::getSupportedSanitizers() const {
+  SanitizerMask Res = ToolChain::getSupportedSanitizers();
+  Res |= SanitizerKind::SafeStack;
+  return Res;
+}
+
 /// DragonFly - DragonFly tool chain which can call as(1) and ld(1) directly.
 
 DragonFly::DragonFly(const Driver &D, const llvm::Triple &Triple,
                      const ArgList &Args)
     : Generic_ELF(D, Triple, Args) {
 
   // Path mangling to find libexec
   getProgramPaths().push_back(getDriver().getInstalledDir());

cfe/trunk/test/Driver/fuchsia.c

 // CHECK-SHARED-NOT: "-pie"
 // CHECK-SHARED: "-shared"
 
 // RUN: %clang %s -### --target=x86_64-unknown-fuchsia -r 2>&1 \
 // RUN:     | FileCheck %s -check-prefix=CHECK-RELOCATABLE
 // CHECK-RELOCATABLE-NOT: "-pie"
 // CHECK-RELOCATABLE-NOT: "--build-id"
 // CHECK-RELOCATABLE: "-r"
+
+// RUN: %clang %s -### --target=x86_64-unknown-fuchsia \
+// RUN:     -fsanitize=safe-stack 2>&1 \
+// RUN:     | FileCheck %s -check-prefix=CHECK-SAFESTACK
+// CHECK-SAFESTACK: "-fsanitize=safe-stack"