The fixdep tool needs to be built before everything else, because it fixes
every object dependency file.

We handle this currently by making all objects to depend on fixdep, which is
error prone and is easily forgotten when new object is added.

Instead of this, this patch force fixdep tool to be built as the first target
in the separate make session. This way we don't need to handle extra fixdep
dependencies and we are certain there's no fixdep race with any parallel make
job.

Committer notes:

Testing it:

Before:

  $ rm -rf /tmp/build/perf/ ; mkdir -p /tmp/build/perf ; make -k O=/tmp/build/perf -C tools/perf install-bin
  make: Entering directory '/home/acme/git/linux/tools/perf'
    BUILD:   Doing 'make -j4' parallel build

  Auto-detecting system features:
  ...                         dwarf: [ on  ]
  ...            dwarf_getlocations: [ on  ]
  ...                         glibc: [ on  ]
  ...                          gtk2: [ on  ]
  ...                      libaudit: [ on  ]
  ...                        libbfd: [ on  ]
  ...                        libelf: [ on  ]
  ...                       libnuma: [ on  ]
  ...        numa_num_possible_cpus: [ on  ]
  ...                       libperl: [ on  ]
  ...                     libpython: [ on  ]
  ...                      libslang: [ on  ]
  ...                     libcrypto: [ on  ]
  ...                     libunwind: [ on  ]
  ...            libdw-dwarf-unwind: [ on  ]
  ...                          zlib: [ on  ]
  ...                          lzma: [ on  ]
  ...                     get_cpuid: [ on  ]
  ...                           bpf: [ on  ]

    GEN      /tmp/build/perf/common-cmds.h
    HOSTCC   /tmp/build/perf/fixdep.o
    HOSTLD   /tmp/build/perf/fixdep-in.o
    LINK     /tmp/build/perf/fixdep
    MKDIR    /tmp/build/perf/pmu-events/
    HOSTCC   /tmp/build/perf/pmu-events/json.o
    MKDIR    /tmp/build/perf/pmu-events/
    HOSTCC   /tmp/build/perf/pmu-events/jsmn.o
    HOSTCC   /tmp/build/perf/pmu-events/jevents.o
    HOSTLD   /tmp/build/perf/pmu-events/jevents-in.o
    PERF_VERSION = 4.9.rc8.g868cd5
    CC       /tmp/build/perf/perf-read-vdso32
  <SNIP>

After:

  $ rm -rf /tmp/build/perf/ ; mkdir -p /tmp/build/perf ; make -k O=/tmp/build/perf -C tools/perf install-bin
  make: Entering directory '/home/acme/git/linux/tools/perf'
    BUILD:   Doing 'make -j4' parallel build
    HOSTCC   /tmp/build/perf/fixdep.o
    HOSTLD   /tmp/build/perf/fixdep-in.o
    LINK     /tmp/build/perf/fixdep

  Auto-detecting system features:
  ...                         dwarf: [ on  ]
  ...            dwarf_getlocations: [ on  ]
  ...                         glibc: [ on  ]
  ...                          gtk2: [ on  ]
  ...                      libaudit: [ on  ]
  ...                        libbfd: [ on  ]
  ...                        libelf: [ on  ]
  ...                       libnuma: [ on  ]
  ...        numa_num_possible_cpus: [ on  ]
  ...                       libperl: [ on  ]
  ...                     libpython: [ on  ]
  ...                      libslang: [ on  ]
  ...                     libcrypto: [ on  ]
  ...                     libunwind: [ on  ]
  ...            libdw-dwarf-unwind: [ on  ]
  ...                          zlib: [ on  ]
  ...                          lzma: [ on  ]
  ...                     get_cpuid: [ on  ]
  ...                           bpf: [ on  ]

    GEN      /tmp/build/perf/common-cmds.h
    MKDIR    /tmp/build/perf/fd/
    CC       /tmp/build/perf/fd/array.o
    LD       /tmp/build/perf/fd/libapi-in.o
    MKDIR    /tmp/build/perf/fs/
    CC       /tmp/build/perf/event-parse.o
    CC       /tmp/build/perf/fs/fs.o
    PERF_VERSION = 4.9.rc8.g57a92f
    CC       /tmp/build/perf/event-plugin.o
    MKDIR    /tmp/build/perf/fs/
    CC       /tmp/build/perf/fs/tracing_path.o
  <SNIP>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1481030331-31944-3-git-send-email-jolsa@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>