macOS high sierra

xx/test: git clone https://github.com/cs50/libcs50.git
then all things done.
xx/test: cd libcs50/
xx/test: sudo make install

cc -Wall -Wextra -Werror -pedantic -std=c99 -fPIC -shared -Wl,-install_name,libcs50-8.1.2.dylib -o libcs50-8.1.2.dylib src/cs50.c
ln -sf libcs50-8.dylib libcs50.dylib
mkdir -p build/include build/lib build/src
install -m 644 src/cs50.c build/src
install -m 644 src/cs50.h build/include
mv libcs50-8.1.2.dylib libcs50.dylib build/lib
cc -Wall -Wextra -Werror -pedantic -std=c99 -fPIC -shared -Wl,-install_name,libcs50-8.1.2.dylib -o libcs50-8.1.2.dylib src/cs50.c
ln -sf libcs50-8.dylib libcs50.dylib
mkdir -p build/include build/lib build/src
install -m 644 src/cs50.c build/src
install -m 644 src/cs50.h build/include
mv libcs50-8.1.2.dylib libcs50.dylib build/lib
mkdir -p /usr/local/src /usr/local/lib /usr/local/include /usr/local/share/man/man3
cp -r build/include build/lib build/src /usr/local
cp: build/lib/libcs50.dylib: No such file or directory

Something wrong with my operation?