[PATCH v3 4/7] debian/rules: support parallel build

[Eric Wong <e@80x24.org>]

This bit stolen from the debian/rules file of `git'
speeds up builds from ~35s to ~10s for me.

Signed-off-by: Eric Wong <e@80x24.org>
---
 debian/rules | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/debian/rules b/debian/rules
index 6631b10..f26271e 100755
--- a/debian/rules
+++ b/debian/rules
@@ -9,6 +9,16 @@ DEB_CFLAGS_MAINT_PREPEND = -Wall
 include /usr/share/dpkg/default.mk
 include /usr/share/dpkg/buildtools.mk
 
+# taken from the debian/rules of src:git
+ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
+  NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
+  MAKEFLAGS += -j$(NUMJOBS)
+  # Setting this with a pattern-specific rule prevents -O from
+  # affecting the top-level make, which would break realtime build
+  # output (unless dh is run as +dh, which causes other problems).
+  %: MAKEFLAGS += -O
+endif
+
 export CC
 
 lib := liburing1