a bug for libc++abi1 package

All files belong to package libc++abi1 are as followed:
/.
/usr
/usr/lib
/usr/lib/x86_64-linux-gnu
/usr/lib/x86_64-linux-gnu/libc++abi.so.1.0
/usr/share
/usr/share/doc
/usr/share/doc/libc++abi1
/usr/share/doc/libc++abi1/changelog.Debian.gz
/usr/share/doc/libc++abi1/copyright
/usr/lib/x86_64-linux-gnu/libc++abi.so.1

but Symbol link "/usr/lib/x86_64-linux-gnu/libc++abi.so" is missing. So if I try to use command "clang++ -stdlib=libc++ main.cpp" to compile a c++ source file, it will report:
/usr/bin/ld: cannot find -lc++abi
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Please repair it. Thanks. By the way, my system is ubuntu 18.04