configs/olimex_a33_olinuxino: U-Boot needs pylibfdt

The U-Boot configuration for the olimex_a33_olinuxino needs pylibfdt,
and therefore needs host-swig. Without this, the build fails with:

  unable to execute 'swig': No such file or directory
  error: command 'swig' failed with exit status 1
  scripts/dtc/pylibfdt/Makefile:27: recipe for target 'scripts/dtc/pylibfdt/_libfdt.so' failed

Fixes:

  https://gitlab.com/buildroot.org/buildroot/-/jobs/269139202

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
diff --git a/configs/olimex_a33_olinuxino_defconfig b/configs/olimex_a33_olinuxino_defconfig
index c71bdb1..71b1669 100644
--- a/configs/olimex_a33_olinuxino_defconfig
+++ b/configs/olimex_a33_olinuxino_defconfig
@@ -18,6 +18,7 @@
 BR2_TARGET_UBOOT_CUSTOM_VERSION_VALUE="2019.04"
 BR2_TARGET_UBOOT_BOARD_DEFCONFIG="A33-OLinuXino"
 BR2_TARGET_UBOOT_NEEDS_DTC=y
+BR2_TARGET_UBOOT_NEEDS_PYLIBFDT=y
 BR2_TARGET_UBOOT_FORMAT_BIN=y
 BR2_TARGET_UBOOT_SPL=y
 BR2_TARGET_UBOOT_SPL_NAME="u-boot-sunxi-with-spl.bin"