【问题解决】报错：unable to execute ‘swig‘: No such file or directory

在编译uboot代码时， make -f rockpi4.mk u-boot -j4

报了以下错误。

  HOSTCC  scripts/dtc/dtc.o
  SHIPPED scripts/dtc/pylibfdt/libfdt.i
  ENVT    include/generated/environment.h
  PYMOD   rebuild
  HOSTCC  scripts/dtc/flattree.o
  UPD     include/generated/version_autogenerated.h
===================== WARNING ======================
This board uses CONFIG_SPL_FIT_GENERATOR. Please migrate
to binman instead, to avoid the proliferation of
arch-specific scripts with no tests.
====================================================
  CFGCHK  u-boot.cfg
unable to execute 'swig': No such file or directory
error: command 'swig' failed with exit status 1
make[3]: *** [scripts/dtc/pylibfdt/Makefile:30: rebuild] Error 1
make[2]: *** [scripts/Makefile.build:398: scripts/dtc/pylibfdt] Error 2
make[2]: *** Waiting for unfinished jobs....
  CC      lib/asm-offsets.s
  CC      arch/arm/lib/asm-offsets.s
  OFCHK   .config
  UPD     include/generated/asm-offsets.h
  UPD     include/generated/generic-asm-offsets.h
  LDS     u-boot.lds
make[1]: *** [Makefile:2035: scripts_dtc] Error 2
make[1]: Leaving directory '/home/test/workspace/code/optee_rk/u-boot'
make: *** [rockpi4.mk:109: u-boot] Error 2
test@test-21:~/workspace/code/optee_rk/build$ cd .

解决方法：
sudo apt install swig