tools/format-cpp: run `xargs` with `-P$(nproc)` (format in parallel)

This saves many seconds per run.

Note that some implementations of xargs might not accept the `-P`
option, therefore `tools/format-cpp` now requires something like
GNU xargs.

`nproc` is also a GNU (Coreutils) thing.

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Change-Id: Ie7113dae32cff506b716c3b590bbe58eac5f1586
Reviewed-on: https://review.lttng.org/c/babeltrace/+/9950
Reviewed-by: Simon Marchi <simon.marchi@efficios.com>
Reviewed-by: Michael Jeanson <mjeanson@efficios.com>

diff --git a/tools/format-cpp b/tools/format-cpp
index 98e901aaff86b4a256dd263b5ef4308e25f71f1c..0a165a8f2b18e03953120bf81ab5ec4030ec52a1 100755 (executable)
--- a/tools/format-cpp
+++ b/tools/format-cpp
@@ -39,7 +39,7 @@ format_cpp() {
        find "$root_dir" \( -name '*.cpp' -o -name '*.hpp' \) \
                ! -wholename '*/cpp-common/optional.hpp' \
                ! -wholename '*/cpp-common/string_view.hpp' \
-               -print0 | xargs -n1 -0 $formatter
+               -print0 | xargs -P$(nproc) -n1 -0 $formatter
 }
 
 if [[ -n "$FORMATTER" ]]; then