Fix Ada bootstrap on Cygwin64

This fixes two compilation errors preventing bootstrap with Ada
on x86_64-pc-cygwin.

2020-05-04  Mikael Pettersson  <mikpelinux@gmail.com>

	PR bootstrap/94918
	* mingw32.h: Prevent windows.h from including emmintrin.h on Cygw64.
	* s-oscons-tmplt.c (Serial_Port_Descriptor): Use System.Win32.HANDLE
	also on Cygwin.

gcc/ada/ChangeLog

+2020-05-04  Mikael Pettersson  <mikpelinux@gmail.com>
+
+	PR bootstrap/94918
+	* mingw32.h: Prevent windows.h from including emmintrin.h on Cygwin64.
+	* s-oscons-tmplt.c (Serial_Port_Descriptor): Use System.Win32.HANDLE
+	also on Cygwin.
+
 2020-03-11  Richard Wai  <richard@annexi-strayline.com>
 
 	* gcc-interface/decl.c (gnat_to_gnu_entity): Also test Is_Public on

gcc/ada/mingw32.h

@@ -56,6 +56,7 @@
 /* Note: windows.h on cygwin-64 includes x86intrin.h which uses malloc.
    That fails to compile, if malloc is poisoned, i.e. if !IN_RTS.  */
 #define _X86INTRIN_H_INCLUDED
+#define _EMMINTRIN_H_INCLUDED
 #endif
 #include <windows.h>
 

gcc/ada/s-oscons-tmplt.c

@@ -261,7 +261,7 @@ main (void) {
 TXT("--  This is the version for " TARGET)
 TXT("")
 TXT("with Interfaces.C;")
-#if defined (__MINGW32__)
+#if defined (__MINGW32__) || defined (__CYGWIN__)
 # define TARGET_OS "Windows"
 # define Serial_Port_Descriptor "System.Win32.HANDLE"
 TXT("with System.Win32;")