Document that override_find_program works on configure_file [skip ci]

Also link to the release notes snippet from the Reference manual

docs/markdown/Reference-manual.md

@@ -1396,11 +1396,12 @@ the following methods.
   /path/to/meson.py introspect`. The user is responsible for splitting
   the string to an array if needed.
 
-- `override_find_program(progname, program)` specifies that whenever
-  `find_program` is used to find a program named `progname`, Meson
-  should not not look it up on the system but instead return
-  `program`, which may either be the result of `find_program` or
-  `configure_file`.
+- `override_find_program(progname, program)` [*(Added
+  0.46.0)*](Release-notes-for-0-46-0.html#Can-override-find_program)
+  specifies that whenever `find_program` is used to find a program
+  named `progname`, Meson should not not look it up on the system but
+  instead return `program`, which may either be the result of
+  `find_program` or `configure_file`.
 
 - `project_version()` returns the version string specified in `project` function call.
 

docs/markdown/snippets/find-override.md

@@ -25,3 +25,13 @@ genprog = find_program('mycodegen')
 
 Now `genprog` points to the custom script. If the dependency had come
 from the system, then it would point to the system version.
+
+You can also use the return value of `configure_file()` to override
+a program in the same way as above:
+
+```meson
+prog_script = configure_file(input : 'script.sh.in',
+                             output : 'script.sh',
+                             configuration : cdata)
+meson.override_find_program('mycodegen', prog_script)
+```