add exception tag to build flags

Author: mariopesch

py/circuitpy_mpconfig.mk

@@ -428,6 +428,10 @@ CFLAGS += -DCIRCUITPY_RE=$(CIRCUITPY_RE)
 CIRCUITPY_REQUIRE_I2C_PULLUPS ?= 1
 CFLAGS += -DCIRCUITPY_REQUIRE_I2C_PULLUPS=$(CIRCUITPY_REQUIRE_I2C_PULLUPS)
 
+# Allow the use of strapping pins for i2c
+CIRCUITPY_I2C_ALLOW_STRAPPING_PINS ?= 0
+CFLAGS += -DCIRCUITPY_I2C_ALLOW_STRAPPING_PINS=$(CIRCUITPY_I2C_ALLOW_STRAPPING_PINS)
+
 # CIRCUITPY_RP2PIO is handled in the raspberrypi tree.
 # Only for rp2 chips.
 # Assume not a rp2 build.