include: Add stdarg.h header.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=54263

include/Makefile.in

@@ -512,6 +512,7 @@ SOURCES = \
 	msvcrt/setjmp.h \
 	msvcrt/share.h \
 	msvcrt/signal.h \
+	msvcrt/stdarg.h \
 	msvcrt/stdbool.h \
 	msvcrt/stddef.h \
 	msvcrt/stdint.h \

include/msvcrt/stdarg.h

@@ -0,0 +1,31 @@
+/*
+ * Variable argument definitions
+ *
+ * Copyright 2022 Jacek Caban
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
+ */
+
+#ifndef _INC_STDARG
+#define _INC_STDARG
+
+#include <vadefs.h>
+
+#define va_start(v,l)  _crt_va_start(v,l)
+#define va_arg(v,l)    _crt_va_arg(v,l)
+#define va_end(v)      _crt_va_end(v)
+#define va_copy(d,s)   _crt_va_copy(d,s)
+
+#endif /* _INC_STDARG */