[cxx-interop] CxxShim files became arch-independent

This adjusts the Windows installation logic after the changes in swiftlang/swift#66765

rdar://110788977

Author: egorzhdan

platforms/Windows/sdk.wxs

@@ -417,11 +417,11 @@
 
     <ComponentGroup Id="libcxxshim">
       <Component Directory="WindowsSDK_usr_lib_swift_windows_ARCH" Id="libcxxshim.h">
-        <File Id="libcxxshim.h" Source="$(var.SDK_ROOT)\usr\lib\swift\windows\$(var.ArchArchDir)\libcxxshim.h" Checksum="yes" KeyPath="yes" />
+        <File Id="libcxxshim.h" Source="$(var.SDK_ROOT)\usr\lib\swift\windows\libcxxshim.h" Checksum="yes" KeyPath="yes" />
       </Component>
 
       <Component Directory="WindowsSDK_usr_lib_swift_windows_ARCH" Id="libcxxshim.modulemap">
-        <File Id="libcxxshim.modulemap" Source="$(var.SDK_ROOT)\usr\lib\swift\windows\$(var.ArchArchDir)\libcxxshim.modulemap" Checksum="yes" KeyPath="yes" />
+        <File Id="libcxxshim.modulemap" Source="$(var.SDK_ROOT)\usr\lib\swift\windows\libcxxshim.modulemap" Checksum="yes" KeyPath="yes" />
       </Component>
     </ComponentGroup>