[LEDE-DEV] latest master fails to build

[Mauro Mozzarelli]

I just pulled the latest from master and the build fails with the following:

g++-uc  -Os -pipe -mno-branch-likely -mips32r2 -mtune=24kc 
-fno-caller-saves -fno-plt -fhonour-copts 
-Wno-error=unused-but-set-variable -Wno-error=unused-result -msoft-float 
-mips16 -minterlink-mips16 
-iremap/sto/router/lede/master-ipvs/build_dir/target-mips_24kc_musl/unrar-5.6.1-bin/unrar:unrar 
-Wformat -Werror=format-security -fstack-protector -D_FORTIFY_SOURCE=1 
-Wl,-z,now -Wl,-z,relro 
-I/sto/router/lede/master-ipvs/staging_dir/target-mips_24kc_musl/usr/include 
-I/sto/router/lede/master-ipvs/staging_dir/target-mips_24kc_musl/include 
-I/sto/router/lede/master-ipvs/staging_dir/toolchain-mips_24kc_gcc-7.3.0_musl/usr/include 
-I/sto/router/lede/master-ipvs/staging_dir/toolchain-mips_24kc_gcc-7.3.0_musl/include/fortify 
-I/sto/router/lede/master-ipvs/staging_dir/toolchain-mips_24kc_gcc-7.3.0_musl/include 
-D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -DRAR_SMP -DUNRAR -c rar.cpp
make[4]: g++-uc: Command not found
makefile:132: recipe for target 'rar.o' failed
make[4]: *** [rar.o] Error 127
make[4]: Leaving directory 
'/sto/router/lede/master-ipvs/build_dir/target-mips_24kc_musl/unrar-5.6.1-bin/unrar'
Makefile:99: recipe for target 
'/sto/router/lede/master-ipvs/build_dir/target-mips_24kc_musl/unrar-5.6.1-bin/unrar/.built' 
failed

I am building under Ubuntu 16.04.1

Do I have to install any extra package? And which one?

apt-cache search g++-uc returns nothing, although I understand g++-uc 
should be part of the openwrt build toolkit, rather than any Ubuntu package.