Print all detected features when VF=1

[qmonnet]

Kernel file tools/build/Makefile.feature has

ifeq ($(VF),1)
  feature_display := 1
  feature_verbose := 1
endif

causing all features to be displayed:

$ VF=1 make

Auto-detecting system features:
...                         clang-bpf-co-re: [ on  ]
...                                    llvm: [ on  ]
...                                  libcap: [ on  ]
...                                  libbfd: [ on  ]
...                          libbfd-liberty: [ on  ]
...                        libbfd-liberty-z: [ on  ]
...                  disassembler-four-args: [ on  ]
...                disassembler-init-styled: [ on  ]
...                             libelf-zstd: [ on  ]

It could be useful for debugging features detection to have the same in this repository. We already have V=1, which prints the details of the detection, but this list is more succinct. On the other hand, it's also used in the kernel repo to force displaying the values when they would otherwise be skipped:

# The $(feature_display) controls the default detection message
# output. It's set if:
# - detected features differes from stored features from
#   last build (in $(FEATURE_DUMP_FILENAME) file)
# - one of the $(FEATURE_DISPLAY) is not detected
# - VF is enabled

but we don't have this issue in the GitHub repo, given that we don't dump features to a file and always print those in FEATURE_DISPLAY. Still, supporting VF=1 could be nice.