fix the path to the python binaries in MacOS

This commit makes the MacOS build script more robust so that it's able
to survive when GitHub updates their MacOS shared runners python version
(and deletes the old python binaires).

For more info, see:

 * BusKill/buskill-app@ec4a023
 * https://github.com/buskill/buskill-app/compare/abbb7a4415f0184e4594623d02b6386f856e2fb5..ec4a0239589cfa7b87432cb2e98e0db886abfaa5
 * BusKill/buskill-app#15 (comment)

build/mac/buildDmg.sh

@@ -11,17 +11,17 @@ set -x
 #
 # Authors: Michael Altfield <michael@buskill.in>
 # Created: 2020-06-22
-# Updated: 2020-09-17
-# Version: 0.2
+# Updated: 2021-01-30
+# Version: 0.3
 ################################################################################
 
 
 ############
 # SETTINGS #
 ############
 
-PYTHON_PATH="`find /usr/local/Cellar/python@3.7 -type f -name python3.7 | head -n1`"
-PIP_PATH="`find /usr/local/Cellar/python@3.7 -type f -name pip3.7 | head -n1`"
+PYTHON_PATH="`find /usr/local/Cellar/python@3* -type f -wholename *bin/python3* | sort -n | uniq | head -n1`"
+PIP_PATH="`find /usr/local/Cellar/python@3* -type f -wholename *bin/pip3* | sort -n | uniq | head -n1`"
 APP_NAME='helloWorld'
 
 PYTHON_VERSION="`${PYTHON_PATH} --version | cut -d' ' -f2`"