makepanda: fix locating UCRT when building with Windows SDK 7.1A

[skip ci]

makepanda/makepandacore.py

@@ -2789,7 +2789,7 @@ def SetupVisualStudioEnviron():
 
     # Targeting the 7.1 SDK (which is the only way to have Windows XP support)
     # with Visual Studio 2015 requires use of the Universal CRT.
-    if winsdk_ver == '7.1' and SDK["VISUALSTUDIO_VERSION"] >= (14,0):
+    if winsdk_ver in ('7.1', '7.1A') and SDK["VISUALSTUDIO_VERSION"] >= (14,0):
         win_kit = GetRegistryKey("SOFTWARE\\Microsoft\\Windows Kits\\Installed Roots", "KitsRoot10")
 
         # Fallback in case we can't read the registry.