Can't build on MacOS Mojave 10.14.5

[hudrima1]

Hi, the build configuration stops with the following error:
buildconf: m4 version not recognized. You need a GNU m4 installed!

I installed m4 with "brew install m4" successfully.
The xcode commandline tools are installed.
XCode is on version 10.2.1
Both build scripts for Android and iOS fail.

Do you have any idea what could solve this problem?
Regards
Marcus