windows returns EINVAL for fopen when there is an asterisk in the name

closes #508

src/error.cpp

@@ -42,6 +42,7 @@ const char *err_str(Error err) {
         case ErrorUnknownArchitecture: return "unrecognized architecture";
         case ErrorUnknownOperatingSystem: return "unrecognized operating system";
         case ErrorUnknownABI: return "unrecognized C ABI";
+        case ErrorInvalidFilename: return "invalid filename";
     }
     return "(invalid error)";
 }

src/error.hpp

@@ -44,6 +44,7 @@ enum Error {
     ErrorUnknownArchitecture,
     ErrorUnknownOperatingSystem,
     ErrorUnknownABI,
+    ErrorInvalidFilename,
 };
 
 const char *err_str(Error err);

src/os.cpp

@@ -1099,7 +1099,7 @@ Error os_fetch_file_path(Buf *full_path, Buf *out_contents, bool skip_shebang) {
             case EINTR:
                 return ErrorInterrupted;
             case EINVAL:
-                zig_unreachable();
+                return ErrorInvalidFilename;
             case ENFILE:
             case ENOMEM:
                 return ErrorSystemResources;