[PATCH v3 1/1] kbuild: deb-pkg: Build parallely with current dpkg-buildpackage

[Bastian Germann <bage@linutronix.de>]

With dpkg-buildpackage v1.21.10 or later, the only way to build the
deb-pkg generated package parallely is adding -j<N> to the MAKEFLAGS
environment variable or using the --jobs-force option, see dpkg commit
1d0ea9b2ba3f ("dpkg-buildpackage: Change -j, --jobs semantics to
non-force mode"). The package ignores the usual parallel build option
that is described in Debian Policy.

Derive make's -j parameter from the DEB_BUILD_OPTIONS environment variable
that ends up being set by dpkg-buildpackage -j<N>. The snippet is copied
from Debian Policy.

Link: https://www.debian.org/doc/debian-policy/ch-source.html#debian-rules-and-deb-build-options
Signed-off-by: Bastian Germann <bage@linutronix.de>
---
 scripts/package/mkdebian | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/scripts/package/mkdebian b/scripts/package/mkdebian
index f74380036bb5..ed5c2b65798b 100755
--- a/scripts/package/mkdebian
+++ b/scripts/package/mkdebian
@@ -238,6 +238,11 @@ fi
 cat <<EOF > debian/rules
 #!$(command -v $MAKE) -f
 
+ifneq (,\$(filter parallel=%,\$(DEB_BUILD_OPTIONS)))
+	NUMJOBS = \$(patsubst parallel=%,%,\$(filter parallel=%,\$(DEB_BUILD_OPTIONS)))
+	MAKEFLAGS += -j\$(NUMJOBS)
+endif
+
 srctree ?= .
 
 build-indep:
-- 
2.39.2