Use wide character startup

Mingw crt-git 12.0.0.r369.g0d4221712-1 now prohibits "command line
contains characters that are not supported in the active code page".
https://sourceforge.net/p/mingw-w64/mingw-w64/ci/0d42217123d3aec0341b79f6d959c76e09648a1e/

Already Ruby builds `argv` in `rb_w32_sysinit`, instead of mswin- or
mingw-made `argv`.  Just bypass the conversion in mingw crt.

Author: nobu

cygwin/GNUmakefile.in

@@ -2,6 +2,8 @@ gnumake = yes
 
 include Makefile
 
+override EXE_LDFLAGS += -municode
+
 DLLWRAP = @DLLWRAP@ --target=$(target_os) --driver-name="$(CC)"
 ifeq (@USE_LLVM_WINDRES@,yes) # USE_LLVM_WINDRES
 	# llvm-windres fails when preprocessor options are added
@@ -69,7 +71,7 @@ $(PROGRAM): $(RUBY_INSTALL_NAME).res.$(OBJEXT)
 $(WPROGRAM): $(RUBYW_INSTALL_NAME).res.$(OBJEXT)
 	@rm -f $@
 	$(ECHO) linking $@
-	$(Q) $(PURIFY) $(CC) -mwindows -e $(SYMBOL_PREFIX)mainCRTStartup $(LDFLAGS) $(XLDFLAGS) \
+	$(Q) $(PURIFY) $(CC) -municode -mwindows -e $(SYMBOL_PREFIX)mainCRTStartup $(LDFLAGS) $(XLDFLAGS) \
 	  $(MAINOBJ) $(EXTOBJS) $(LIBRUBYARG) $(LIBS) -o $@
 $(STUBPROGRAM): $(RUBY_INSTALL_NAME).res.$(OBJEXT)
 

main.c

@@ -57,3 +57,7 @@ main(int argc, char **argv)
     ruby_sysinit(&argc, &argv);
     return rb_main(argc, argv);
 }
+
+#ifdef _WIN32
+int wmain(void) {return main(0, NULL);}
+#endif