Make the windows builder more bit-aware

builders/windows-builder.py

@@ -110,6 +110,7 @@ Portable App Builds
 
 import os
 import glob
+import sys
 from distutils import dir_util
 from shutil import copy, move, rmtree
 
@@ -267,6 +268,8 @@ class WindowsBuilder(Builder):
         super().setup_system_paths()
         self.python_root = os.path.dirname(self.python)
         self.site_packages = os.path.join(self.python_root, 'Lib', 'site-packages')
+        # Default program_files to 'Program Files (x86)' - the folder for 32-bit programs on 64-bit systems, if that
+        # does not exists the host system is 32-bit so fallback to 'Program Files'.
         self.program_files = os.getenv('PROGRAMFILES(x86)')
         if not self.program_files:
             self.program_files = os.getenv('PROGRAMFILES')
@@ -331,8 +334,11 @@ class WindowsBuilder(Builder):
         Return a list of any extra parameters we wish to use
         """
         parameters = []
+        # Detect python instance bit size
+        arch = 'x86' if sys.maxsize == 0x7fffffff else 'x64'
+        dll_path = '{pf}\\Windows Kits\\10\\Redist\\ucrt\\DLLs\\{arch}\\*.dll'.format(pf=self.program_files, arch=arch)
         # Finds the UCRT DDLs available from the Windows 10 SDK
-        for binary in glob.glob('C:\\Program Files (x86)\\Windows Kits\\10\\Redist\\ucrt\\DLLs\\x64\\*.dll'):
+        for binary in glob.glob(dll_path):
             parameters.append('--add-binary')
             parameters.append(binary + ";.")
         return parameters