[RISCV] Default to -fsanitize=shadow-call-stack for Fuchsia

The ShadowCallStack is the preferred and default ABI for Fuchsia.

Reviewed By: phosek

Differential Revision: https://reviews.llvm.org/D143357

Author: frobtech

clang/lib/Driver/ToolChains/Fuchsia.cpp

@@ -466,13 +466,13 @@ SanitizerMask Fuchsia::getDefaultSanitizers() const {
   SanitizerMask Res;
   switch (getTriple().getArch()) {
   case llvm::Triple::aarch64:
+  case llvm::Triple::riscv64:
     Res |= SanitizerKind::ShadowCallStack;
     break;
   case llvm::Triple::x86_64:
     Res |= SanitizerKind::SafeStack;
     break;
   default:
-    // TODO: Enable SafeStack on RISC-V once tested.
     break;
   }
   return Res;

clang/test/Driver/fuchsia.c

@@ -31,6 +31,7 @@
 // CHECK: "-isysroot" "[[SYSROOT:[^"]+]]"
 // CHECK: "-internal-externc-isystem" "[[SYSROOT]]{{/|\\\\}}include"
 // CHECK-AARCH64: "-fsanitize=shadow-call-stack"
+// CHECK-RISCV64: "-fsanitize=shadow-call-stack"
 // CHECK-X86_64: "-fsanitize=safe-stack"
 // CHECK: "-stack-protector" "2"
 // CHECK-AARCH64: "-target-feature" "+outline-atomics"