Para quaisquer sketches dos ESP8266 (e nodeMCU), ao compilar aparecem as mensagens seguintes:

In file included from c:\...arduino15\packages\esp8266\tools\xtensa-1x106-elf-gcc\1.20.0-26-gb404fb9-2\xtensa-1x106-elf\include\_ansi.h:16:0,
from c:\...arduino15\packages\esp8266\tools\................................................................................................................\stdlib,h:11,
from c:\...arduino15\packages\esp8266\hardware\esp8266\2.2.0\cores\esp8266/Arduino.h:27,
from sketch\PISCA_NODEMCU.INO.CPP:1:
C:\documents and settings\..............\arduino15\packages\esp8266\tools\xtensa-1x106-elf-gcc\1.20.0-26-gb404fb9-2\xtensa-1x106-elf\include\sys\config.h:170:36:
Fatal error: xtensa/config/core-isa.h: No such file or directory.
#include <xtensa/config/core-isa.h>
compilation terminated.
exit status 1
Erro compilando para a placa NodeMCU 0.9 (ESP-12 Module)

PISCA_NODEMCU é o nome do sketch em questão. Para o blink com o ESP8266
aparecem as mesmas mensagens.
Alguém pode me ajudar?