gen_compile_commands: Allow the line prefix to still be cmd_

Builds in tools still use the cmd_ prefix in .cmd files, so don't
require the saved part. Name the groups in the line pattern match so
that changing the regular expression is more robust and works with the
addition of a new match group.

Signed-off-by: Ian Rogers <irogers@google.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Yang Jihong <yangjihong1@huawei.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: llvm@lists.linux.dev
Cc: Ming Wang <wangming01@loongson.cn>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Tom Rix <trix@redhat.com>
Cc: bpf@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-perf-users@vger.kernel.org
Link: https://lore.kernel.org/r/20231009183920.200859-2-irogers@google.com


Signed-off-by: Namhyung Kim <namhyung@kernel.org>