[WebAssembly] Simplify --help message

[sbc100]

Summary

Update wasm to match ELF changes made rL333596.

[ruiu]

LGTM

lld/trunk/wasm/Options.td

 include "llvm/Option/OptParser.td"
 
 // For options whose names are multiple letters, either one dash or
 // two can precede the option name except those that start with 'o'.
 class F<string name>: Flag<["--", "-"], name>;
 class J<string name>: Joined<["--", "-"], name>;
 class S<string name>: Separate<["--", "-"], name>;
 
-multiclass Eq<string name> {
-  def "": Separate<["--", "-"], name>;
-  def _eq: Joined<["--", "-"], name # "=">, Alias<!cast<Separate>(NAME)>;
+multiclass Eq<string name, string help> {
+  def NAME: Separate<["--", "-"], name>;
+  def NAME # _eq: Joined<["--", "-"], name # "=">, Alias<!cast<Separate>(NAME)>,
+    HelpText<help>;
 }
 
 multiclass B<string name, string help1, string help2> {
   def NAME: Flag<["--", "-"], name>, HelpText<help1>;
   def no_ # NAME: Flag<["--", "-"], "no-" # name>, HelpText<help2>;
 }
 
 // The follow flags are shared with the ELF linker

 def relocatable: F<"relocatable">, HelpText<"Create relocatable object file">;
 
 def strip_all: F<"strip-all">, HelpText<"Strip all symbols">;
 
 def strip_debug: F<"strip-debug">, HelpText<"Strip debugging information">;
 
 def threads: F<"threads">, HelpText<"Run the linker multi-threaded">;
 
-defm undefined: Eq<"undefined">,
-  HelpText<"Force undefined symbol during linking">;
+defm undefined: Eq<"undefined", "Force undefined symbol during linking">;
 
 def v: Flag<["-"], "v">, HelpText<"Display the version number">;
 
 def verbose: F<"verbose">, HelpText<"Verbose mode">;
 
 def version: F<"version">, HelpText<"Display the version number and exit">;
 
 def z: JoinedOrSeparate<["-"], "z">, MetaVarName<"<option>">,
   HelpText<"Linker option extensions">;
 
 // The follow flags are unique to wasm
 
 def allow_undefined: F<"allow-undefined">,
   HelpText<"Allow undefined symbols in linked binary">;
 
 def allow_undefined_file: J<"allow-undefined-file=">,
   HelpText<"Allow symbols listed in <file> to be undefined in linked binary">;
 
 def allow_undefined_file_s: Separate<["-"], "allow-undefined-file">,
   Alias<allow_undefined_file>;
 
-defm export: Eq<"export">,
-  HelpText<"Force a symbol to be exported">;
+defm export: Eq<"export", "Force a symbol to be exported">;
 
 def export_all: F<"export-all">,
   HelpText<"Export all symbols (normally combined with --no-gc-sections)">;
 
 def export_table: F<"export-table">,
   HelpText<"Export function table to the environment">;
 
 def global_base: J<"global-base=">,

 def lto_O: J<"lto-O">, MetaVarName<"<opt-level>">,
   HelpText<"Optimization level for LTO">;
 def lto_partitions: J<"lto-partitions=">,
   HelpText<"Number of LTO codegen partitions">;
 def disable_verify: F<"disable-verify">;
 def save_temps: F<"save-temps">;
 def thinlto_cache_dir: J<"thinlto-cache-dir=">,
   HelpText<"Path to ThinLTO cached object file directory">;
-defm thinlto_cache_policy: Eq<"thinlto-cache-policy">,
-  HelpText<"Pruning policy for the ThinLTO cache">;
+defm thinlto_cache_policy: Eq<"thinlto-cache-policy", "Pruning policy for the ThinLTO cache">;
 def thinlto_jobs: J<"thinlto-jobs=">, HelpText<"Number of ThinLTO jobs">;