[clang] Move XCore specific options from Clang.cpp to XCore.cpp

[MaskRay]

LGTM.

clang/lib/Driver/ToolChains/Clang.cpp

if (Args.hasFlag(options::OPT_fshort_enums, options::OPT_fno_short_enums,
     CmdArgs.push_back("-fshort-enums");
 
   RenderCharacterOptions(Args, AuxTriple ? *AuxTriple : RawTriple, CmdArgs);
 
   // -fuse-cxa-atexit is default.
   if (!Args.hasFlag(
           options::OPT_fuse_cxa_atexit, options::OPT_fno_use_cxa_atexit,
           !RawTriple.isOSAIX() && !RawTriple.isOSWindows() &&
-              TC.getArch() != llvm::Triple::xcore &&
               ((RawTriple.getVendor() != llvm::Triple::MipsTechnologies) ||
                RawTriple.hasEnvironment())) ||
       KernelOrKext)
     CmdArgs.push_back("-fno-use-cxa-atexit");
 
   if (Args.hasFlag(options::OPT_fregister_global_dtors_with_atexit,
                    options::OPT_fno_register_global_dtors_with_atexit,
                    RawTriple.isOSDarwin() && !KernelOrKext))

clang/lib/Driver/ToolChains/XCore.cpp

if (const char *cl_include_dir = getenv("XCC_C_INCLUDE_PATH")) {
     addSystemIncludes(DriverArgs, CC1Args, DirVec);
   }
 }
 
 void XCoreToolChain::addClangTargetOptions(const ArgList &DriverArgs,
                                            ArgStringList &CC1Args,
                                            Action::OffloadKind) const {
   CC1Args.push_back("-nostdsysteminc");
+  // Set `-fno-use-cxa-atexit` to default.
+  if (!DriverArgs.hasFlag(options::OPT_fuse_cxa_atexit,
+                          options::OPT_fno_use_cxa_atexit, false))
+    CC1Args.push_back("-fno-use-cxa-atexit");
 }
 
 void XCoreToolChain::AddClangCXXStdlibIncludeArgs(
     const ArgList &DriverArgs, ArgStringList &CC1Args) const {
   if (DriverArgs.hasArg(clang::driver::options::OPT_nostdinc) ||
       DriverArgs.hasArg(options::OPT_nostdlibinc) ||
       DriverArgs.hasArg(options::OPT_nostdincxx))
     return;

clang/test/Driver/xcore-opts.c

 // RUN: %clang -target xcore %s -g -Wl,L1Arg,L2Arg -Wa,A1Arg,A2Arg -fverbose-asm -v -### -o %t.o 2>&1 | FileCheck %s
 // RUN: %clang -target xcore -x c++ %s -g -Wl,L1Arg,L2Arg -Wa,A1Arg,A2Arg -fverbose-asm -v -### -o %t.o 2>&1 | FileCheck %s
 // RUN: %clang -target xcore -x c++ %s -fexceptions -### -o %t.o 2>&1 | FileCheck -check-prefix CHECK-EXCEP %s
 // RUN: %clang -target xcore %s -g0 -### -o %t.o 2>&1 | FileCheck -check-prefix CHECK-G0 %s
 
 // CHECK: "-mframe-pointer=none"
-// CHECK: "-nostdsysteminc"
+// CHECK: "-nostdsysteminc" "-fno-use-cxa-atexit"
 // CHECK: "-fno-signed-char"
-// CHECK: "-fno-use-cxa-atexit"
 // CHECK-NOT: "-fcxx-exceptions"
 // CHECK-NOT: "-fexceptions"
 // CHECK-NOT: "-fcommon"
 // CHECK: xcc" "-o"
 // CHECK-NOT: "-fexceptions"
 // CHECK: "-c" "-v" "-g" "-fverbose-asm" "A1Arg" "A2Arg"
 // CHECK: xcc" "-o"
 // CHECK-NOT: "-fexceptions"
 // CHECK: "-v"
 // CHECK: "L1Arg" "L2Arg"
 
 // CHECK-EXCEP: "-fno-use-cxa-atexit"
 // CHECK-EXCEP: "-fcxx-exceptions"
 // CHECK-EXCEP: "-fexceptions"
 // CHECK-EXCEP-NOT: "-fcommon"
 // CHECK-EXCEP: xcc" "-o"
 // CHECK-EXCEP-NOT: "-fexceptions"
 // CHECK-EXCEP: xcc" "-o"
 // CHECK-EXCEP: "-fexceptions"
 
 // CHECK-G0: xcc"
 // CHECK-G0-NOT: "-g"
 // CHECK-G0: xcc"
-