add the out keyword argument to universal functions (#621)

* add optional out keyword argument to math functions

* fix the keyword handling in sqrt

* run micropython build on ubuntu 20.04 instead of latest

* fix unused variable error in vector_generic_vector

Author: v923z

.github/workflows/build.yml

@@ -19,7 +19,7 @@ jobs:
     strategy:
         matrix:
             os:
-                - ubuntu-latest
+                - ubuntu-20.04
                 - macOS-latest
             dims: [1, 2, 3, 4]
     runs-on: ${{ matrix.os }}