ppa: move build to /tmp

ppa/Makefile

 all:
 	# Clean.
-	rm -rf build
+	rm -rf /tmp/build
 
 	# Prepare to build source packages.
 	sudo apt-get install -y git dpkg-dev devscripts dput
-	mkdir -p build
+	mkdir -p /tmp/build
 
 	# POSTGREY
 
 	# Download our fork of the Debian postgrey package.
-	git clone https://github.com/mail-in-a-box/postgrey build/postgrey
+	git clone https://github.com/mail-in-a-box/postgrey /tmp/build/postgrey
 
 	# Download the corresponding upstream package.
-	wget -O build/postgrey_1.35.orig.tar.gz http://postgrey.schweikert.ch/pub/postgrey-1.35.tar.gz
+	wget -O /tmp/build/postgrey_1.35.orig.tar.gz http://postgrey.schweikert.ch/pub/postgrey-1.35.tar.gz
 
 	# Build the source package.
 	sudo apt-get build-dep -y postgrey
-	(cd build/postgrey; dpkg-source -b .)
-	(cd build/postgrey; dpkg-buildpackage -S -us -uc -nc)
+	(cd /tmp/build/postgrey; dpkg-source -b .)
+	(cd /tmp/build/postgrey; dpkg-buildpackage -S -us -uc -nc)
 
 	# Sign the packages.
-	debsign build/postgrey_1.35-1miab1_source.changes
+	debsign /tmp/build/postgrey_1.35-1miab1_source.changes
 
 	# Upload to PPA.
-	dput ppa:mail-in-a-box/ppa build/postgrey_1.35-1miab1_source.changes
+	dput ppa:mail-in-a-box/ppa /tmp/build/postgrey_1.35-1miab1_source.changes
 
 	# Clear the intermediate files.
-	rm -rf build/postgrey
+	rm -rf /tmp/build/postgrey