scripts: not hardcode MSYSTEM (#1739)

scripts/innosetup/innosetup.iss.in

@@ -26,12 +26,16 @@ AppPublisherURL={#MyAppURL}
 AppSupportURL={#MyAppURL}
 AppUpdatesURL={#MyAppURL}
 
-#if Arch=="x64"
-  ArchitecturesAllowed=x64
-  ArchitecturesInstallIn64BitMode=x64
-  #define ArchInternal "x86_64"
-#else
+#if Arch=="x86"
   #define ArchInternal "i686"
+#else
+  ArchitecturesAllowed={#Arch}
+  ArchitecturesInstallIn64BitMode={#Arch}
+  #if Arch=="x64"
+    #define ArchInternal "x86_64"
+  #elif Arch=="arm64"
+    #define ArchInternal "aarch64"
+  #endif
 #endif
 
 AllowNoIcons=yes

scripts/innosetup/innosetup.sh

@@ -29,13 +29,24 @@ main() {
   local version
   local output
 
-  if [[ $MSYSTEM == "MINGW64" ]]; then
+  case "$MSYSTEM" in
+    MINGW64|UCRT64|CLANG64)
     arch=x64
     arch_file=x86_64
-  else
-    arch=i686;
+    ;;
+    MINGW32|CLANG32)
+    arch=x86
     arch_file=i686
-  fi
+    ;;
+    CLANGARM64)
+    arch=arm64
+    arch_file=aarch64
+    ;;
+    *)
+    echo "error: unsupported MSYSTEM type: $MSYSTEM"
+    exit 1
+    ;;
+  esac
 
   initial_arg_count=$#