output/jack: enable on Windows

This enables the JACK output plugin on Windows, but doesn't link
against libjack64.dll, instead loads the DLL at runtime with
LoadLibrary().  This kludge avoids the extremely fragile JACK shared
memory protocol by using the system's libjack64.dll, without requiring
the same DLL at build time.

python/build/libs.py

@@ -9,6 +9,7 @@ from build.autotools import AutotoolsProject
 from build.ffmpeg import FfmpegProject
 from build.openssl import OpenSSLProject
 from build.boost import BoostProject
+from build.jack import JackProject
 
 libmpdclient = MesonProject(
     'https://www.musicpd.org/download/libmpdclient/2/libmpdclient-2.19.tar.xz',
@@ -443,6 +444,12 @@ libnfs = AutotoolsProject(
     autoreconf=True,
 )
 
+jack = JackProject(
+    'https://github.com/jackaudio/jack2/archive/v1.9.17.tar.gz',
+    '38f674bbc57852a8eb3d9faa1f96a0912d26f7d5df14c11005ad499c8ae352f2',
+    'lib/pkgconfig/jack.pc',
+)
+
 boost = BoostProject(
     'https://dl.bintray.com/boostorg/release/1.75.0/source/boost_1_75_0.tar.bz2',
     '953db31e016db7bb207f11432bef7df100516eeb746843fa0486a222e3fd49cb',