tools build: Fix rust feature detection

Features in FEATURE_TESTS_BASIC will be set as being available if
test-all.c builds, so since the rust test isn't included in test-all.c,
we can't have 'rust' in there, remove it from FEATURE_TESTS_BASIC and
use feature-check so that it tries to build test-rust.bin, doing the
actual feature detection.

On a system lacking a rust compiler:

  Makefile.config:1158: Rust is not found. Test workloads with rust are disabled.

  Auto-detecting system features:
  ...                                   libdw: [ on  ]
  ...                                   glibc: [ on  ]
  ...                                  libelf: [ on  ]
  ...                                 libnuma: [ on  ]
  ...                  numa_num_possible_cpus: [ on  ]
  ...                               libpython: [ on  ]
  ...                             libcapstone: [ on  ]
  ...                               llvm-perf: [ on  ]
  ...                                    zlib: [ on  ]
  ...                                    lzma: [ on  ]
  ...                                     bpf: [ on  ]
  ...                                  libaio: [ on  ]
  ...                                 libzstd: [ on  ]
  ...                              libopenssl: [ on  ]
  ...                                    rust: [ OFF ]

  $ cat /tmp/build/perf-tools-next/feature/test-rust.make.output
  /bin/sh: line 1: rustc: command not found
  $ file /tmp/build/perf-tools-next/feature/test-rust.bin
  /tmp/build/perf-tools-next/feature/test-rust.bin: cannot open `/tmp/build/perf-tools-next/feature/test-rust.bin' (No such file or directory)
  $
  $ perf -vv | grep RUST
                  rust: [ OFF ]  # HAVE_RUST_SUPPORT
  $

And after installing it:

  ...                                    rust: [ on  ]

  $ cat /tmp/build/perf-tools-next/feature/test-rust.make.output
  $ file /tmp/build/perf-tools-next/feature/test-rust.bin
/tmp/build/perf-tools-next/feature/test-rust.bin: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, BuildID[sha1]=9c416edf673ee3705b97bae893a99a6fcf1ee258, for GNU/Linux 3.2.0, with debug_info, not stripped
  $
  $ perf -vv | grep RUST
                  rust: [ on  ]  # HAVE_RUST_SUPPORT
  $

Fixes: 6a32fa5c ("tools build: Add a feature test for rust compiler")
Cc: Dmitrii Dolgov <9erthalion6@gmail.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>