esp32: Add support for esp32c6.

This commit adds general support for ESP32-C6 SoCs.

Signed-off-by: Andrew Leech <andrew@alelec.net>
diff --git a/ports/esp32/esp32_common.cmake b/ports/esp32/esp32_common.cmake
index e59e2dc..2c81e8c 100644
--- a/ports/esp32/esp32_common.cmake
+++ b/ports/esp32/esp32_common.cmake
@@ -198,7 +198,7 @@
 set(MICROPY_TARGET ${COMPONENT_TARGET})
 
 # Define mpy-cross flags, for use with frozen code.
-if(NOT IDF_TARGET STREQUAL "esp32c3")
+if(CONFIG_IDF_TARGET_ARCH STREQUAL "xtensa")
 set(MICROPY_CROSS_FLAGS -march=xtensawin)
 endif()