scripts/pahole-flags.sh: Parse DWARF and generate BTF with multithreading.

Pass a "-j" argument to pahole if possible to reduce the time of generating BTF info. Since v1.22, pahole can parse DWARF and generate BTF with multithreading to speed up the conversion. It will reduce the overall build time of the kernel for seconds. v3 fixes whitespaces and improves the commit description. v2 checks the version of pahole to enable multithreading only if possible. [v2] https://lore.kernel.org/bpf/20220216193431.2691015-1-kuifeng@fb.com/ [v1] https://lore.kernel.org/bpf/20220216004616.2079689-1-kuifeng@fb.com/ Signed-off-by: Kui-Feng Lee <kuifeng@fb.com> Acked-by: Yonghong Song <yhs@fb.com>

Author: Kui-Feng Lee

scripts/pahole-flags.sh

@@ -16,5 +16,8 @@ fi
 if [ "${pahole_ver}" -ge "121" ]; then
 extra_paholeopt="${extra_paholeopt} --btf_gen_floats"
 fi
+if [ "${pahole_ver}" -ge "122" ]; then
+extra_paholeopt="${extra_paholeopt} -j"
+fi
 
 echo ${extra_paholeopt}