libmakepkg: util/pkgbuild.sh needs processing on build

pkgbuild.sh contained @DEBUGSUFFIX@ and so needs to be run through the sed
command on build.

Signed-off-by: Allan McRae <allan@archlinux.org>

scripts/Makefile.am

@@ -50,7 +50,6 @@ LIBMAKEPKGDIRS = \
 LIBMAKEPKG = \
 	libmakepkg/util/message.sh \
 	libmakepkg/util/option.sh \
-	libmakepkg/util/pkgbuild.sh \
 	libmakepkg/util/util.sh
 
 LIBMAKEPKG_IN = \
@@ -92,6 +91,7 @@ LIBMAKEPKG_IN = \
 	libmakepkg/tidy/upx.sh \
 	libmakepkg/tidy/zipman.sh \
 	libmakepkg/util.sh \
+	libmakepkg/util/pkgbuild.sh \
 	libmakepkg/util/source.sh
 
 LIBMAKEPKG_DIST = \