Use a rough equivalent of realpath

realpath(1) is not available on macOS.

(Funny, because realpath(3) originated in FreeBSD, so it came to macOS
before Linux adopted it, but Linux beat macOS to realpath(1).)

scripts/setup_bls_build_flags.sh

@@ -11,7 +11,9 @@ gopath=$(go env GOPATH)
 # HMY_PATH is the common root directory of all harmony repos
 HMY_PATH="${gopath%%:*}/src/github.com/harmony-one"
 if [ ! -d $HMY_PATH ]; then
-   HMY_PATH=$(realpath $progdir/../..)
+   # "env pwd" uses external pwd(1) implementation and not the Bash built-in,
+   # which does not fully dereference symlinks.
+   HMY_PATH=$(cd $progdir/../.. && env pwd)
 fi
 : ${OPENSSL_DIR="/usr/local/opt/openssl"}
 : ${MCL_DIR="${HMY_PATH}/mcl"}