This does appear to be a packaging bug.
I added run-script-os:
yarn add run-script-os
Then added this into the scripts section of my package.json:
"install": "run-script-os",
"install:linux": "find node_modules/@fusioncharts -type f -exec sed -i 's|../../../fc-utils|../../../utils|g' {} \\;",
"install:darwin": "find node_modules/@fusioncharts -type f -exec sed -i '' 's|../../../fc-utils|../../../utils|g' {} \\;"
Things work great after that. (The only reason for run-script-os is because sed is implemented differently on Linux and Mac (which draws from NeXT heritage) and so need slightly different arguments.