tools/makectx: Use subprocess to direct output file

This way it will appear in 'ctx.h' and not (blah).

Also update the .gitignore for *.obj files, which interestingly
the preprocessor spat out after testing locally.

.gitignore

@@ -6,4 +6,8 @@ ISLE.EXE
 LEGO1.DLL
 build/
 *.swp
+
+# Stuff generated by the preprocessor and/or tools/makectx.py
 *.i
+*.obj
+ctx.h

tools/makectx.py

@@ -1,15 +1,29 @@
 #!/usr/bin/python3
 import argparse
 import os
+import subprocess
 
-parser = argparse.ArgumentParser(allow_abbrev=False,
+parser = argparse.ArgumentParser(
-  description='Verify Exports: Compare the exports of two DLLs.')
+    allow_abbrev=False, description="Verify Exports: Compare the exports of two DLLs."
-parser.add_argument('cppfile', metavar='cppfile', help='Path to the C++ File to preprocess.')
+)
+parser.add_argument(
+    "cppfile", metavar="cppfile", help="Path to the C++ File to preprocess."
+)
+parser.add_argument(
+    "--debug",
+    action="store_true",
+    help="Print debug information by showing the output from the preprocessor. THIS WILL TAKE A LONG TIME AS YOUR TERMINAL TRIES TO LOAD OVER 100K LINES OF TEXT. Use this if your context contains an error or is empty.",
+)
 
 args = parser.parse_args()
 if not os.path.isfile(args.cppfile):
-  parser.error('Specified C++ file does not exist.')
+    parser.error("Specified C++ file does not exist.")
 
-os.system('cl.exe /EP /P ' + args.cppfile)
+output = subprocess.run(
+    "cl.exe /EP " + args.cppfile, capture_output=not args.debug, text=True
+)
 
-print('Preprocessed file. It will be in the directory you executed in this command as "(filename).i".')
+f = open("ctx.h", "w")
+f.write(output.stdout)
+
+print("Preprocessed file to ctx.h")