Build System.Native for AIX/i (#11896)

This will probably be needed in the future; and attempts to solve
the issue with System.Random not working when running under Jenkins.

configure.ac

@@ -5905,6 +5905,22 @@ elif test x$host_linux = xyes; then
 	AC_MSG_RESULT(linux)
 
 	MONO_NATIVE_PLATFORM_TYPE="MONO_NATIVE_PLATFORM_TYPE_LINUX"
+elif case $host_os in aix*|os400*) true;; *) false;; esac; then
+	mono_native_text="AIX"
+	MONO_NATIVE_CC=$CC
+	MONO_NATIVE_CXX=$CXX
+	MONO_NATIVE_CPPFLAGS=$CPPFLAGS
+	MONO_NATIVE_CXXFLAGS=$CXXFLAGS
+	MONO_NATIVE_CFLAGS=$CFLAGS
+	MONO_NATIVE_LDFLAGS=$LDFLAGS
+
+	mono_native=yes
+	mono_native_compat=no
+	MONO_NATIVE_PLATFORM=aix
+	AC_MSG_CHECKING([Mono.Native support])
+	AC_MSG_RESULT(aix)
+
+	MONO_NATIVE_PLATFORM_TYPE="MONO_NATIVE_PLATFORM_TYPE_AIX"
 else
 	mono_native=no
 	mono_native_text="no"
@@ -5937,6 +5953,7 @@ AM_CONDITIONAL(MONO_NATIVE_COMPAT, test x$mono_native_compat = xyes)
 AM_CONDITIONAL(MONO_NATIVE_PLATFORM_MACOS, test x$MONO_NATIVE_PLATFORM = xmacos)
 AM_CONDITIONAL(MONO_NATIVE_PLATFORM_IOS, test x$MONO_NATIVE_PLATFORM = xios)
 AM_CONDITIONAL(MONO_NATIVE_PLATFORM_LINUX, test x$MONO_NATIVE_PLATFORM = xlinux)
+AM_CONDITIONAL(MONO_NATIVE_PLATFORM_AIX, test x$MONO_NATIVE_PLATFORM = xaix)
 
 MONO_NATIVE_PLATFORM_TYPE_COMPAT="$MONO_NATIVE_PLATFORM_TYPE | MONO_NATIVE_PLATFORM_TYPE_COMPAT"
 MONO_NATIVE_PLATFORM_TYPE_UNIFIED="$MONO_NATIVE_PLATFORM_TYPE | MONO_NATIVE_PLATFORM_TYPE_UNIFIED"

mcs/class/corlib/Mono/MonoNativePlatformType.cs

@@ -35,6 +35,7 @@ enum MonoNativePlatformType
 		MONO_NATIVE_PLATFORM_TYPE_MACOS		= 1,
 		MONO_NATIVE_PLATFORM_TYPE_IOS		= 2,
 		MONO_NATIVE_PLATFORM_TYPE_LINUX		= 3,
+		MONO_NATIVE_PLATFORM_TYPE_AIX		= 4,
 
 		MONO_NATIVE_PLATFORM_TYPE_IPHONE	= 0x100,
 		MONO_NATIVE_PLATFORM_TYPE_TV		= 0x200,

mono/native/mono-native-platform.h

@@ -2,13 +2,14 @@
 
 #include "mono/utils/mono-publib.h"
 
-// Keep in sync with mcs/class/System/Mono/MonoNativePlatformType.cs
+// Keep in sync with mcs/class/corlib/Mono/MonoNativePlatformType.cs
 
 typedef enum {
 	MONO_NATIVE_PLATFORM_TYPE_UNKNOWN	= 0,
 	MONO_NATIVE_PLATFORM_TYPE_MACOS		= 1,
 	MONO_NATIVE_PLATFORM_TYPE_IOS		= 2,
 	MONO_NATIVE_PLATFORM_TYPE_LINUX		= 3,
+	MONO_NATIVE_PLATFORM_TYPE_AIX		= 4,
 
 	MONO_NATIVE_PLATFORM_TYPE_IPHONE	= 0x100,
 	MONO_NATIVE_PLATFORM_TYPE_TV		= 0x200,