Update framework-kendryte-standalone-sdk version and builder script

[maxgerhardt]

Recent projects like https://github.com/kendryte/kendryte-standalone-demo/tree/develop/face_detect cannot be compiled under PlatformIO because the SDK (https://github.com/kendryte/kendryte-standalone-sdk) package it uses has become outdated with respect to the master branch, and so, errors like

src\image_process.c:18:10: fatal error: iomem.h: No such file or directory

are encountered. Sadly Sipeed doesn't seem to be making regular releases of the SDK anymore (V0.5.6 is from May 2019) but the SDK is still being further developed.

This PR mainly updates the builder script builder/frameworks/kendryte-standalone-sdk.py to adapt to the new SDK version and compilation settings. It also incorporates PR #39 because otherwise a Python error occurs. It also changes the version of framework-kendryte-standalone-sdk to point directly to the git version, however, after a merge this should changed back to a stable package version together with an updated version of that package (CC @ivankravets).

A test project that showcases working compilation with this updated version and non-working of it with the current version is located at https://github.com/maxgerhardt/pio-kendryte-facedetect-demo.

This stems from a user's post about not being able to compile the reference project at https://community.platformio.org/t/kendryte-face-detect-example-with-sipeed-maix-bit/24763.

Also linked to #31.