Platform: don't crash EmscriptenApplication on a WebGL-less build.

The code right below is querying the `log` option, which wasn't added.
Becomes a problem when Magnum is compiled w/o GL support, e.g. for a
custom WebGPU renderer.

src/Magnum/Platform/EmscriptenApplication.cpp

@@ -238,7 +238,11 @@ EmscriptenApplication::EmscriptenApplication(const Arguments& arguments, NoCreat
     #ifdef MAGNUM_TARGET_GL
     _context.emplace(NoCreate, args, arguments.argc, arguments.argv);
     #else
-    args.parse(arguments.argc, arguments.argv);
+    /** @todo this is duplicated here, in Sdl2Application and in
+        GlfwApplication, figure out a nice non-duplicated way to handle this */
+    args.addOption("log", "default").setHelp("log", "console logging", "default|quiet|verbose")
+        .setFromEnvironment("log")
+        .parse(arguments.argc, arguments.argv);
     #endif
 
     /* Save command-line arguments */

src/Magnum/Platform/GlfwApplication.cpp

@@ -81,8 +81,9 @@ GlfwApplication::GlfwApplication(const Arguments& arguments, NoCreateT):
     #ifdef MAGNUM_TARGET_GL
     _context.emplace(NoCreate, args, arguments.argc, arguments.argv);
     #else
-    /** @todo this is duplicated here and in Sdl2Application, figure out a nice
-        non-duplicated way to handle this */
+    /** @todo this is duplicated here, in Sdl2Application and in
+        EmscriptenApplication, figure out a nice non-duplicated way to handle
+        this */
     args.addOption("log", "default").setHelp("log", "console logging", "default|quiet|verbose")
         .setFromEnvironment("log")
         .parse(arguments.argc, arguments.argv);

src/Magnum/Platform/Sdl2Application.cpp

@@ -126,8 +126,9 @@ Sdl2Application::Sdl2Application(const Arguments& arguments, NoCreateT):
     #ifdef MAGNUM_TARGET_GL
     _context.emplace(NoCreate, args, arguments.argc, arguments.argv);
     #else
-    /** @todo this is duplicated here and in GlfwApplication, figure out a nice
-        non-duplicated way to handle this */
+    /** @todo this is duplicated here, in GlfwApplication and in
+        EmscriptenApplication, figure out a nice non-duplicated way to handle
+        this */
     args.addOption("log", "default").setHelp("log", "console logging", "default|quiet|verbose")
         .setFromEnvironment("log")
         .parse(arguments.argc, arguments.argv);