bpo-36941: Windows build changes for Windows ARM64 (GH-13365)

diff --git a/PCbuild/_decimal.vcxproj b/PCbuild/_decimal.vcxproj
index fa4bb8d..465a7ad 100644
--- a/PCbuild/_decimal.vcxproj
+++ b/PCbuild/_decimal.vcxproj
@@ -5,6 +5,10 @@
       <Configuration>Debug</Configuration>
       <Platform>ARM</Platform>
     </ProjectConfiguration>
+    <ProjectConfiguration Include="Debug|ARM64">
+      <Configuration>Debug</Configuration>
+      <Platform>ARM64</Platform>
+    </ProjectConfiguration>
     <ProjectConfiguration Include="Debug|Win32">
       <Configuration>Debug</Configuration>
       <Platform>Win32</Platform>
@@ -17,6 +21,10 @@
       <Configuration>PGInstrument</Configuration>
       <Platform>ARM</Platform>
     </ProjectConfiguration>
+    <ProjectConfiguration Include="PGInstrument|ARM64">
+      <Configuration>PGInstrument</Configuration>
+      <Platform>ARM64</Platform>
+    </ProjectConfiguration>
     <ProjectConfiguration Include="PGInstrument|Win32">
       <Configuration>PGInstrument</Configuration>
       <Platform>Win32</Platform>
@@ -29,6 +37,10 @@
       <Configuration>PGUpdate</Configuration>
       <Platform>ARM</Platform>
     </ProjectConfiguration>
+    <ProjectConfiguration Include="PGUpdate|ARM64">
+      <Configuration>PGUpdate</Configuration>
+      <Platform>ARM64</Platform>
+    </ProjectConfiguration>
     <ProjectConfiguration Include="PGUpdate|Win32">
       <Configuration>PGUpdate</Configuration>
       <Platform>Win32</Platform>
@@ -41,6 +53,10 @@
       <Configuration>Release</Configuration>
       <Platform>ARM</Platform>
     </ProjectConfiguration>
+    <ProjectConfiguration Include="Release|ARM64">
+      <Configuration>Release</Configuration>
+      <Platform>ARM64</Platform>
+    </ProjectConfiguration>
     <ProjectConfiguration Include="Release|Win32">
       <Configuration>Release</Configuration>
       <Platform>Win32</Platform>
@@ -80,6 +96,7 @@
       <PreprocessorDefinitions>_CRT_SECURE_NO_WARNINGS;MASM;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <PreprocessorDefinitions Condition="'$(Platform)' == 'Win32'">CONFIG_32;PPRO;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <PreprocessorDefinitions Condition="'$(Platform)'=='ARM'">CONFIG_32;ANSI;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions Condition="'$(Platform)'=='ARM64'">CONFIG_64;ANSI;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <PreprocessorDefinitions Condition="'$(Platform)' == 'x64'">CONFIG_64;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <AdditionalIncludeDirectories>..\Modules\_decimal;..\Modules\_decimal\libmpdec;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
     </ClCompile>
@@ -124,6 +141,7 @@
     <CustomBuild Include="..\Modules\_decimal\libmpdec\vcdiv64.asm">
       <ExcludedFromBuild Condition="'$(Platform)'=='Win32'">true</ExcludedFromBuild>
       <ExcludedFromBuild Condition="'$(Platform)'=='ARM'">true</ExcludedFromBuild>
+      <ExcludedFromBuild Condition="'$(Platform)'=='ARM64'">true</ExcludedFromBuild>
       <Command>ml64 /nologo /c /Zi /Fo "$(IntDir)vcdiv64.obj" "%(FullPath)"</Command>
       <Outputs>$(IntDir)vcdiv64.obj;%(Outputs)</Outputs>
     </CustomBuild>