remove compile flag for risc-v MCUs which is only valid for xtensa MCUs

[Jason2866]

Description:

simplify and less error prone setup for all MCUs.
Small refactor of strip-floats.py

Checklist:

• The pull request is done against the latest development branch
• Only relevant files were touched
• Only one feature/fix was added per PR and the code change compiles without warnings
• The code change is tested and works with Tasmota core ESP8266 V.2.7.6
• The code change is tested and works with Tasmota core ESP32 V.3.0.1
• I accept the CLA.

NOTE: The code change must pass CI tests. Your PR cannot be merged unless tests pass