openssl/ssl.h not found but installed with homebrew

Try put these in your bash or zsh profile.

export PATH="/usr/local/opt/[email protected]/bin:$PATH"
export LDFLAGS="-L/usr/local/opt/[email protected]/lib"
export CPPFLAGS="-I/usr/local/opt/[email protected]/include"
export PKG_CONFIG_PATH="/usr/local/opt/[email protected]/lib/pkgconfig"

I found the solution: clang was not looking in the right place.

xcode-select --install

This post resolved this issue: On mac, g++ (clang) fails to search /usr/local/include and /usr/local/lib by default