Allow using doxytag2zealdb for docset generation

This allows to generate docsets on Linux too and not only macOS as
before, when it required Xcode.

Closes https://github.com/wxWidgets/wxWidgets/pull/1343

docs/doxygen/scripts/write_info_tag.py

@@ -0,0 +1,41 @@
+#
+# write_info_tag.py
+# Write a key/value pair to an Info.plist file created by Doxygen
+# while generating docsets.
+#
+# Author: Ian McInerney (https://github.com/imciner2)
+
+import sys
+import plistlib
+
+# The first argument is the plist filename without the extension
+fname = sys.argv[1] + ".plist"
+
+# The second argument is the key to replace
+key = sys.argv[2]
+
+# The thrid argument is the value of the key
+val = sys.argv[3]
+
+# Handle boolean values
+if val.lower() == "true":
+  val = True
+elif val.lower() == "false":
+  val = False
+
+
+if sys.version_info >= (3, 4, 0):
+  # Use the new API if python 3.4 is used
+  with open( fname, 'rb' ) as plist_file:
+    pl = plistlib.load( plist_file )
+
+  pl[key] = val
+
+  with open( fname, 'wb' ) as plist_file:
+    pl = plistlib.dump( pl, plist_file )
+
+else:
+  # Use the old API otherwise (supports python 2.7 as well)
+  pl = plistlib.readPlist( fname )
+  pl[key] = val
+  plistlib.writePlist( pl, fname )