I tried this, and it works.
I still need to enclose them in ’ ’ though, becouse the strings don’t get recognized as strings, if i leave them out.
But it already looks better like this.
build_flags =
'-DWIFI_PASS="verySecretPassword"'
'-DWIFI_SSID="niceWIFIName"'
'-DThingSpeakChannelNumber=0000'
'-DThingSpeakWriteAPIKey="ABCDEF"'