patch 9.1.1499: MS-Windows: no indication of ARM64 architecture

Problem:  MS-Windows: no indication of ARM64 architecture
Solution: Add ARM64 to version output and include in nsis installer
          (RestorerZ)

related: vim/vim-win32-installer#381
closes: #17642

Signed-off-by: RestorerZ <restorer@mail2k.ru>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/nsis/README.txt b/nsis/README.txt
index 4b4b7a0..3bb32d4 100644
--- a/nsis/README.txt
+++ b/nsis/README.txt
@@ -101,6 +101,8 @@
     "HAVE_NLS=0"	— do not add native language support.
     "HAVE_MULTI_LANG=0" — to create an English-only the installer.
     "WIN64=1"		— to create a 64-bit the installer.
+    "ARM64=1"		— to create the installer for ARM64. The WIN64 variable
+			    must be set to 1.
     "X=<scriptcmd>"	— executes scriptcmd in script.  If multiple scriptcmd
 			    are specified, they are separated by a semicolon.
 			    Example "X=OutFile MyVim.exe;XPMode on"