Make sure the correct Gradle is always used during build

Hello,

When a build recipe contains gradle=yes, the Gradle binary specified in config.py is used. But when a build script (a Makefile for example) manually calls gradle, it uses the binary that is in my PATH (which in my case is Gradle 3.2 from Debian Stable and usually not what I need).

Would it be possible to make fdroid build replace all Gradle calls with the binary set in config.py? (Maybe with by setting a custom PATH before the build?)