Revert D135076 "[Clang] Make offloading flags accept '-' and '--'"

[MaskRay]

Summary

This reverts commit 11adae50892e6e94f10ce41bc738a9823a6b3251.
There are multiple aspects this change is not appealing.

• They conflict with JoinedOrSeparate -o. The old exception -objc-* should not be used an excuse.
• We generally want new options to be more rigid and avoid multiple spellings.
• If users get used to -offload-*, a misspelled -offload-* option still gets passed as -o ffloat-* without being detected.

[MaskRay]

Pushed in f6797056fc4163e6fe5bd57bebd19aa7fd83a778

clang/include/clang/Driver/Options.td

 def Xopenmp_target : Separate<["-"], "Xopenmp-target">, Group<CompileOnly_Group>,
   HelpText<"Pass <arg> to the target offloading toolchain.">, MetaVarName<"<arg>">;
 def Xopenmp_target_EQ : JoinedAndSeparate<["-"], "Xopenmp-target=">, Group<CompileOnly_Group>,
   HelpText<"Pass <arg> to the target offloading toolchain identified by <triple>.">,
   MetaVarName<"<triple> <arg>">;
 def z : Separate<["-"], "z">, Flags<[LinkerInput]>,
   HelpText<"Pass -z <arg> to the linker">, MetaVarName<"<arg>">,
   Group<Link_Group>;
-def offload_link : Flag<["--", "-"], "offload-link">, Group<Link_Group>,
+def offload_link : Flag<["--"], "offload-link">, Group<Link_Group>,
   HelpText<"Use the new offloading linker to perform the link job.">;
 def Xlinker : Separate<["-"], "Xlinker">, Flags<[LinkerInput, RenderAsInput]>,
   HelpText<"Pass <arg> to the linker">, MetaVarName<"<arg>">,
   Group<Link_Group>;
 def Xoffload_linker : JoinedAndSeparate<["-"], "Xoffload-linker">,
   HelpText<"Pass <arg> to the offload linkers or the ones idenfied by -<triple>">,
   MetaVarName<"<triple> <arg>">, Group<Link_Group>;
 def Xpreprocessor : Separate<["-"], "Xpreprocessor">, Group<Preprocessor_Group>,

 
 def gpu_use_aux_triple_only : Flag<["--"], "gpu-use-aux-triple-only">,
   InternalDriverOpt, HelpText<"Prepare '-aux-triple' only without populating "
                               "'-aux-target-cpu' and '-aux-target-feature'.">;
 def cuda_include_ptx_EQ : Joined<["--"], "cuda-include-ptx=">, Flags<[NoXarchOption]>,
   HelpText<"Include PTX for the following GPU architecture (e.g. sm_35) or 'all'. May be specified more than once.">;
 def no_cuda_include_ptx_EQ : Joined<["--"], "no-cuda-include-ptx=">, Flags<[NoXarchOption]>,
   HelpText<"Do not include PTX for the following GPU architecture (e.g. sm_35) or 'all'. May be specified more than once.">;
-def offload_arch_EQ : Joined<["--", "-"], "offload-arch=">, Flags<[NoXarchOption]>,
+def offload_arch_EQ : Joined<["--"], "offload-arch=">, Flags<[NoXarchOption]>,
   HelpText<"CUDA offloading device architecture (e.g. sm_35), or HIP offloading target ID in the form of a "
            "device architecture followed by target ID features delimited by a colon. Each target ID feature "
            "is a pre-defined string followed by a plus or minus sign (e.g. gfx908:xnack+:sramecc-).  May be "
            "specified more than once.">;
 def cuda_gpu_arch_EQ : Joined<["--"], "cuda-gpu-arch=">, Flags<[NoXarchOption]>,
   Alias<offload_arch_EQ>;
 def cuda_feature_EQ : Joined<["--"], "cuda-feature=">, HelpText<"Manually specify the CUDA feature to use">;
 def hip_link : Flag<["--"], "hip-link">,
   HelpText<"Link clang-offload-bundler bundles for HIP">;
 def no_hip_rt: Flag<["-"], "no-hip-rt">,
   HelpText<"Do not link against HIP runtime libraries">;
-def no_offload_arch_EQ : Joined<["--", "-"], "no-offload-arch=">, Flags<[NoXarchOption]>,
+def no_offload_arch_EQ : Joined<["--"], "no-offload-arch=">, Flags<[NoXarchOption]>,
   HelpText<"Remove CUDA/HIP offloading device architecture (e.g. sm_35, gfx906) from the list of devices to compile for. "
            "'all' resets the list to its default value.">;
 def emit_static_lib : Flag<["--"], "emit-static-lib">,
   HelpText<"Enable linker job to emit a static library.">;
 def no_cuda_gpu_arch_EQ : Joined<["--"], "no-cuda-gpu-arch=">, Flags<[NoXarchOption]>,
   Alias<no_offload_arch_EQ>;
 def cuda_noopt_device_debug : Flag<["--"], "cuda-noopt-device-debug">,
   HelpText<"Enable device-side debug info generation. Disables ptxas optimizations.">;

 defm autolink : BoolFOption<"autolink",
   CodeGenOpts<"Autolink">, DefaultTrue,
   NegFlag<SetFalse, [CC1Option], "Disable generation of linker directives for automatic library linking">,
   PosFlag<SetTrue>>;
 
 // In the future this option will be supported by other offloading
 // languages and accept other values such as CPU/GPU architectures,
 // offload kinds and target aliases.
-def offload_EQ : CommaJoined<["--", "-"], "offload=">, Flags<[NoXarchOption]>,
+def offload_EQ : CommaJoined<["--"], "offload=">, Flags<[NoXarchOption]>,
   HelpText<"Specify comma-separated list of offloading target triples (CUDA and HIP only)">;
 
 // C++ Coroutines TS
 defm coroutines_ts : BoolFOption<"coroutines-ts",
   LangOpts<"Coroutines">, Default<cpp20.KeyPath>,
   PosFlag<SetTrue, [CC1Option], "Enable support for the C++ Coroutines TS">,
   NegFlag<SetFalse>>;
 
def fopenmp_target_new_runtime : Flag<["-"], "fopenmp-target-new-runtime">,
   Group<f_Group>, Flags<[CC1Option, HelpHidden]>;
 def fno_openmp_target_new_runtime : Flag<["-"], "fno-openmp-target-new-runtime">,
   Group<f_Group>, Flags<[CC1Option, HelpHidden]>;
 defm openmp_optimistic_collapse : BoolFOption<"openmp-optimistic-collapse",
   LangOpts<"OpenMPOptimisticCollapse">, DefaultFalse,
   PosFlag<SetTrue, [CC1Option]>, NegFlag<SetFalse>, BothFlags<[NoArgumentUnused, HelpHidden]>>;
 def static_openmp: Flag<["-"], "static-openmp">,
   HelpText<"Use the static host OpenMP runtime while linking.">;
-def offload_new_driver : Flag<["--", "-"], "offload-new-driver">, Flags<[CC1Option]>, Group<f_Group>,
+def offload_new_driver : Flag<["--"], "offload-new-driver">, Flags<[CC1Option]>, Group<f_Group>,
   MarshallingInfoFlag<LangOpts<"OffloadingNewDriver">>, HelpText<"Use the new driver for offloading compilation.">;
-def no_offload_new_driver : Flag<["--", "-"], "no-offload-new-driver">, Flags<[CC1Option]>, Group<f_Group>,
+def no_offload_new_driver : Flag<["--"], "no-offload-new-driver">, Flags<[CC1Option]>, Group<f_Group>,
   HelpText<"Don't Use the new driver for offloading compilation.">;
-def offload_device_only : Flag<["--", "-"], "offload-device-only">,
+def offload_device_only : Flag<["--"], "offload-device-only">,
   HelpText<"Only compile for the offloading device.">;
-def offload_host_only : Flag<["--", "-"], "offload-host-only">,
+def offload_host_only : Flag<["--"], "offload-host-only">,
   HelpText<"Only compile for the offloading host.">;
-def offload_host_device : Flag<["--", "-"], "offload-host-device">,
+def offload_host_device : Flag<["--"], "offload-host-device">,
   HelpText<"Only compile for the offloading host.">;
 def cuda_device_only : Flag<["--"], "cuda-device-only">, Alias<offload_device_only>,
   HelpText<"Compile CUDA code for device only">;
 def cuda_host_only : Flag<["--"], "cuda-host-only">, Alias<offload_host_only>,
   HelpText<"Compile CUDA code for host only. Has no effect on non-CUDA compilations.">;
 def cuda_compile_host_device : Flag<["--"], "cuda-compile-host-device">, Alias<offload_host_device>,
   HelpText<"Compile CUDA code for both host and device (default). Has no "
            "effect on non-CUDA compilations.">;