After changing my Tasmota ESP8266-dev environment to Visual Studio Code I ran into the problem that I always got the following error when trying to recompile my customized Tasmota firmware:

c:/users/username/.platformio/packages/toolchain-xtensa@1.40802.0/bin/../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/bin/ld.exe: .pio\build\sonoff-sensors\firmware.elf section `.text' will not fit in region `iram1_0_seg'
collect2.exe: error: ld returned 1 exit status
*** [.pio\build\sonoff-sensors\firmware.elf] Error 1

Seems the problem is introduced by the updated Platformio 4 environemnt which ships some updated libraries that do not comply to the ESP-requirements. To work with Platformio 4 it is necessary to adapt the platformio.ini to match the following configuration:

[platformio]
build_dir = .pioenvs

[env:myesp8266env]
platform = espressif8266@1.5.0
... 

https://github.com/platformio/platform-espressif8266/releases/tag/v1.5.0

Discussion on the Github bugtracker for the Tasmota project:
https://github.com/arendst/Sonoff-Tasmota/issues/6073#issuecomment-511111038