[llvm-dlltool] Ignore the --temp-prefix option

llvm-dlltool tolerates unknown options as long as they are plain
flags, but if given the parameter value as a separate argument,
e.g. "--temp-prefix foo", it fails to ignore it.

Differential Revision: https://reviews.llvm.org/D152361

Author: mstorsjo

llvm/lib/ToolDrivers/llvm-dlltool/Options.td

@@ -24,3 +24,6 @@ def S_alias: JoinedOrSeparate<["--"], "as">, Alias<S>;
 
 def f: JoinedOrSeparate<["-"], "f">, HelpText<"Assembler Flags">;
 def f_alias: JoinedOrSeparate<["--"], "as-flags">, Alias<f>;
+
+def t: JoinedOrSeparate<["-"], "t">, HelpText<"Prefix for temporary files (ignored)">;
+def t_alias: JoinedOrSeparate<["--"], "temp-prefix">, Alias<t>;

llvm/test/tools/llvm-dlltool/ignored-opts.def

@@ -0,0 +1,8 @@
+; RUN: llvm-dlltool -m i386 -d %s -l %t.a --temp-prefix foo
+; RUN: llvm-dlltool -m i386 -d %s -l %t.a --temp-prefix=foo
+; RUN: llvm-dlltool -m i386 -d %s -l %t.a -t foo
+; RUN: llvm-dlltool -m i386 -d %s -l %t.a -tfoo
+
+LIBRARY test.dll
+EXPORTS
+TestFunction