Add section to CONFIGURE.md link

Without it, doxygen (at least, version 1.9.8) gives the following error:
unable to resolve reference to '/liboqs/CONFIGURE.md' for \ref command

This makes scripts/run_doxygen.sh return exit code 1 instead of 0, and
causes `ninja gen_docs` to fail

README.md

@@ -104,7 +104,7 @@ In order to optimize support effort,
 		cmake -GNinja ..
 		ninja
 
-Various `cmake` build options to customize the resultant artifacts are available and are [documented in CONFIGURE.md](CONFIGURE.md). All supported options are also listed in the `.CMake/alg-support.cmake` file, and can be viewed by running `cmake -LAH ..` in the `build` directory.
+Various `cmake` build options to customize the resultant artifacts are available and are [documented in CONFIGURE.md](CONFIGURE.md#options-for-configuring-liboqs-builds). All supported options are also listed in the `.CMake/alg-support.cmake` file, and can be viewed by running `cmake -LAH ..` in the `build` directory.
 
 The following instructions assume we are in `build`.