'make test' was successful.
And indeed,
${PETSC_DIR}/${PETSC_ARCH}/lib/petsc/conf/petscvariables
exists.
There was a mistake in my PETSC_DIR.
Now FindPETSc.cmake does find petscvariables ...
... and I am at the next error:
CMake Error at cmake/modules/FindPETSc.cmake:164 (include):
include could not find load file:
ResolveCompilerPaths
smime.p7s
Description: S/MIME Cryptographic Signature
