Try manually adding CXX flag

Author: beiller

build.sh

@@ -12,7 +12,8 @@ fi
 if [ ! -f libsentencepiece.a ]
 then
     tar xzvf v0.1.97.tar.gz
-    cd sentencepiece-0.1.97/ && rm -rf build && mkdir build && cd build && cmake ..
+    cd sentencepiece-0.1.97/ && rm -rf build && mkdir build && cd build
+    cmake -E env CXXFLAGS="-std=c++17" cmake ..
     make sentencepiece-static -j $(nproc)
     cd ../..
     cp sentencepiece-0.1.97/build/src/libsentencepiece.a ./