Update how-to-build.rst - hint for macOS rgd. common strip problem [MANUAL MERGE]

Update how-to-build.rst - Added another hint for macOS, for the common problem that strip fails on mpy-cross with "malformed object (unknown load command 9)"

Documentation/how-to-build.rst

@@ -137,3 +137,6 @@ In order to do a rebuild you can issue a clean command to ninja via
   $ ninja -C build/ -t clean
 
 Otherwise, rerunning ``./bootstrap.sh`` will also clean the build-directory.
+
+.. note:: macOS: If ``strip`` fails to work on the freshly compiled mpy-cross: "strip: object: (...)/lib/micropython/micropython/mpy-cross/mpy-cross malformed object (unknown load command 9)", you a likely not using the `strip` that matches to your ``clang``. Do ``which strip && which clang``, and if the paths don't match, clean up your PATHs, or as a quick hack, create a symlink for strip. 
+

[rahix]

Sorry, this formatting is not quite correct. You need to use:

.. note::

   **macOS**: If ``strip`` fails to work on the freshly compiled ``mpy-cross``:
   "strip: object: (...)/lib/micropython/micropython/mpy-cross/mpy-cross
   malformed object (unknown load command 9)", you a likely not using the
   `strip` that matches to your ``clang``. Do ``which strip && which clang``,
   and if the paths don't match, clean up your PATHs, or as a quick hack,
   create a symlink for strip.

[rahix]

You can test locally by running ./Documentation/build-docs.sh and then see the output in Documentation/output/index.html