package/micropython: libffi is optional, not mandatory

libffi is optional, not mandatory since bump to version 1.22.0 in commit
1e12b7dd49d1c64a5195f226e9e4da21e84f5d0c and
https://github.com/micropython/micropython/commit/89b320737652829edbab921e86d7ad3962d86d9e

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/micropython/Config.in

@@ -2,7 +2,6 @@ config BR2_PACKAGE_MICROPYTHON
 	bool "micropython"
 	depends on BR2_TOOLCHAIN_HAS_THREADS
 	depends on !BR2_STATIC_LIBS
-	select BR2_PACKAGE_LIBFFI
 	help
 	  Micro Python is a lean and fast implementation of the Python
 	  3 programming language that is optimised to run on a

package/micropython/micropython.mk

@@ -12,7 +12,7 @@ MICROPYTHON_SOURCE = micropython-$(MICROPYTHON_VERSION).tar.xz
 # and most of the copied code is not used in the unix build.
 MICROPYTHON_LICENSE = MIT, BSD-1-Clause, BSD-3-Clause, Zlib
 MICROPYTHON_LICENSE_FILES = LICENSE
-MICROPYTHON_DEPENDENCIES = host-pkgconf libffi host-python3
+MICROPYTHON_DEPENDENCIES = host-python3
 MICROPYTHON_CPE_ID_VENDOR = micropython
 
 # Use fallback implementation for exception handling on architectures that don't
@@ -36,6 +36,13 @@ MICROPYTHON_MAKE_OPTS += \
 	LDFLAGS_EXTRA="$(TARGET_LDFLAGS)" \
 	CWARN=
 
+ifeq ($(BR2_PACKAGE_LIBFFI),y)
+MICROPYTHON_DEPENDENCIES += host-pkgconf libffi
+MICROPYTHON_MAKE_OPTS += MICROPY_PY_FFI=1
+else
+MICROPYTHON_MAKE_OPTS += MICROPY_PY_FFI=0
+endif
+
 define MICROPYTHON_BUILD_CMDS
 	$(TARGET_MAKE_ENV) $(MAKE) -C $(@D)/mpy-cross
 	$(TARGET_MAKE_ENV) $(MAKE) -C $(@D)/ports/unix \