perf tools: Create source symlink in perf object dir

perf tools: Create source symlink in perf object dir

Create a source symlink to the original source in the objdir.

This is similar to what the main kernel build script does.

Committer testing:

  ⬢[acme@toolbox perf-tools-next]$ make O=/tmp/build/$(basename $PWD)/ -C tools/perf install-bin
  <SNIP>
  ⬢[acme@toolbox perf-tools-next]$ ls -la /tmp/build/perf-tools-next/source
  lrwxrwxrwx. 1 acme acme 41 Aug  9 16:26 /tmp/build/perf-tools-next/source -> /home/acme/git/perf-tools-next/tools/perf
  ⬢[acme@toolbox perf-tools-next]$

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Ian Rogers <irogers@google.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20240807231823.898979-1-ak@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>