Don't use colons in filenames (#2134)

Windows filenames can't contain colons. Use @ instead for passing arguments to passes.

Author: dschuff

src/passes/ExtractFunction.cpp

@@ -27,7 +27,7 @@ struct ExtractFunction : public Pass {
   void run(PassRunner* runner, Module* module) override {
     Name name = runner->options.getArgument(
       "extract",
-      "ExtractFunction usage:  wasm-opt --pass-arg=extract:FUNCTION_NAME");
+      "ExtractFunction usage:  wasm-opt --pass-arg=extract@FUNCTION_NAME");
     std::cerr << "extracting " << name << "\n";
     bool found = false;
     for (auto& func : module->functions) {

src/tools/optimization-options.h

@@ -142,12 +142,12 @@ struct OptimizationOptions : public ToolOptions {
       .add("--pass-arg",
            "-pa",
            "An argument passed along to optimization passes being run. Must be "
-           "in the form KEY:VALUE",
+           "in the form KEY@VALUE",
            Options::Arguments::N,
            [this](Options*, const std::string& argument) {
-             auto colon = argument.find(':');
+             auto colon = argument.find('@');
              if (colon == std::string::npos) {
-               Fatal() << "--pass-arg value must be in the form of KEY:VALUE";
+               Fatal() << "--pass-arg value must be in the form of KEY@VALUE";
              }
              auto key = argument.substr(0, colon);
              auto value = argument.substr(colon + 1);