Unable to build Bitcoin on Mac Catalina
Berkeley-db from brew which is clang compiled is GCC incompatible. Either Recompile berkeley-db4 with GCC:
HOMEBREW_CC=gcc-10 HOMEBREW_CXX=g++-10 brew reinstall --build-from-source berkeley-db4
or compile Core with clang
Discussion: https://github.com/bitcoin/bitcoin/issues/3228