I was following the instruction from the Youtube video 3 and wanted to build the keytools on a Linux PC.
The build stops at the first file with the message:
*** No rule to make target 'asn.o', needed by 'sign'.

The makefile contains a general rule for building .o files from .c files. This seems not to work.

I haven't modified any file I fetched from Github. So are there some environment settings missing on my PC?