testing/mbuffer: fix license to SPDX, add check, fix install

testing/mbuffer/APKBUILD

@@ -2,11 +2,11 @@
 # Maintainer: Katie Holly <holly@fuslvz.ws>
 pkgname=mbuffer
 pkgver=20171011
-pkgrel=0
+pkgrel=1
 pkgdesc="mbuffer buffers I/O operations and displays the throughput rate"
 url="http://www.maier-komor.de/mbuffer.html"
 arch="all"
-license="GPL-3.0"
+license="GPL-3.0-only"
 depends=""
 makedepends="linux-headers libressl-dev"
 install=""
@@ -26,9 +26,14 @@ build() {
 	make
 }
 
+check() {
+	cd "$builddir"
+	make check TESTTREE=./
+}
+
 package() {
 	cd "$builddir"
-	make DESTDIR="$pkgdir" install
+	make -j1 DESTDIR="$pkgdir" install
 }
 
 sha512sums="398d7545388a94b4f8961193192cd5e1139b84f31c7699c2b7f66b84a40488a2e70c88a2a70578bd95375e11efc87978a5f6fec805dbbc5f1fea460b3a9c68c4  mbuffer-20171011.tgz"