Make .zshrc more flexible for arm64 M1 Macs.

.zshrc

@@ -19,7 +19,7 @@ export PS1=$'\n'"%F{green} %*%F %3~ %F{white}"$'\n'"$ "
 plugins=(git brew history kubectl history-substring-search)
 
 # Custom $PATH with extra locations.
-export PATH=/usr/local/bin:/usr/local/sbin:$HOME/bin:$HOME/go/bin:/usr/local/git/bin:$HOME/.composer/vendor/bin:$PATH
+export PATH=$HOME/Library/Python/3.8/bin:/opt/homebrew/bin:/usr/local/bin:/usr/local/sbin:$HOME/bin:$HOME/go/bin:/usr/local/git/bin:$HOME/.composer/vendor/bin:$PATH
 
 # Bash-style time output.
 export TIMEFMT=$'\nreal\t%*E\nuser\t%*U\nsys\t%*S'
@@ -30,8 +30,18 @@ then
   source ~/.aliases
 fi
 
+# Set architecture-specific brew share path.
+arch_name="$(uname -m)"
+if [ "${arch_name}" = "x86_64" ]; then
+    share_path="/usr/local/share"
+elif [ "${arch_name}" = "arm64" ]; then
+    share_path="/opt/homebrew/share"
+else
+    echo "Unknown architecture: ${arch_name}"
+fi
+
 # Allow history search via up/down keys.
-source /usr/local/share/zsh-history-substring-search/zsh-history-substring-search.zsh
+source ${share_path}/zsh-history-substring-search/zsh-history-substring-search.zsh
 bindkey "^[[A" history-substring-search-up
 bindkey "^[[B" history-substring-search-down