temp/modemmanager: build with a single thread only (MR 1607)

For some reason, the ModemManager build tends to freeze when built
with QEMU user emulation for arm*. Changing the build to use a single
thread only (-j1) avoids that, although the build is slower of course.

Also limit building to "armhf armv7 aarch64" since the forks are not
needed on any other architectures, to reduce build times a bit. The
other architectures can just use the upstream packages from Alpine.

temp/modemmanager/APKBUILD

@@ -6,7 +6,7 @@ _pkgver=1.14.6
 pkgrel=0
 pkgdesc="ModemManager library"
 url="http://www.freedesktop.org/wiki/Software/ModemManager"
-arch="all"
+arch="armhf armv7 aarch64"
 license="GPL-2.0-or-later AND LGPL-2.1-or-later"
 depends_dev="libmm-glib"
 makedepends="$depends_dev gobject-introspection-dev gtk-doc vala
@@ -28,6 +28,10 @@ source="https://www.freedesktop.org/software/ModemManager/ModemManager-$_pkgver.
 	rpmsg-udev.rules"
 builddir="$srcdir"/ModemManager-$_pkgver
 
+# Workaround build freeze with QEMU user emulation
+export JOBS=1
+export MAKEFLAGS=-j$JOBS
+
 build() {
 	# Note: --enable-gtk-doc is disabled to speed up build time
 	./configure \