system/rhash: Fix build on arm

Signed-off-by: Samuel Holland <samuel@sholland.org>

system/rhash/APKBUILD

@@ -27,7 +27,7 @@ check() {
 }
 
 package() {
-	make DESTDIR="$pkgdir" install install-gmo install-lib-headers install-lib-so-link install-man
+	make -j1 DESTDIR="$pkgdir" install install-gmo install-lib-headers install-lib-so-link install-man
 }
 
 sha512sums="9dba4fa4dd49d323f2e440c5b93eac1ef62eb4046ec4ef611f0978c12c1739002f1ac1f1ec5e61bd359dc89e9ed612db71be91a795184ac5d5433280d27fa4c1  rhash-1.3.8.tar.gz"