esp-idf/components/driver/component.mk

#
# Component Makefile
#
COMPONENT_SRCDIRS := . $(IDF_TARGET)

COMPONENT_ADD_INCLUDEDIRS := include $(IDF_TARGET)/include $(IDF_TARGET)/include/driver

COMPONENT_PRIV_INCLUDEDIRS := include/driver

# uses C11 atomic feature
spi_master.o: CFLAGS += -std=gnu11