make install fails for macos and windows

[falkTX]

make[1]: Entering directory '/home/falktx/PawPawBuilds/builds/regrader-port-412e475cef1025d955fae4229b6bc94596f36fd4/plugins/Regrader'
install: cannot stat '../../bin/regrader.lv2/*.so': No such file or directory
Makefile:147: recipe for target 'install' failed
make[1]: *** [install] Error 1

The plugin makefile is using $(LIB_EXT) for most file extensions, but the lv2 binary is wrong.
Works ok after a simple .so change to $(LIB_EXT).

[jpcima]

Fixed in later thanks.
This problem arised from the cookiecutter template, hence most personal projects are also affected so I'm going to fix the whole of them.