wscript: refactor opus wscript files, now it builds only if system package wasn't found

3rdparty/opus/wscript

@@ -0,0 +1,52 @@
+#! /usr/bin/env python
+# encoding: utf-8
+
+import os
+
+OPUS_CHECK='''#include <opus.h>
+#include <stddef.h>
+int main()
+{
+	OpusEncoder *oe = opus_encoder_create(48000, 2, OPUS_APPLICATION_VOIP, NULL);
+	OpusDecoder *od = opus_decoder_create(48000, 2, NULL);
+	return !oe || !od;
+}
+'''
+
+def options(opt):
+	pass
+
+def configure(conf):
+	if conf.check_pkg('opus', 'OPUS', OPUS_CHECK, fatal = False):
+		conf.env.HAVE_OPUS = True
+		return
+
+	if not conf.path.find_dir('opus') or not conf.path.find_dir('opus/src'):
+		conf.fatal('Can\'t find opus submodule. Run `git submodule update --init --recursive`.')
+		return
+
+	# TODO: ARM/x86 intrinsics detection
+	# TODO: maybe call autotools/cmake/meson instead?
+
+def build(bld):
+	if bld.env.HAVE_OPUS:
+		return
+
+	sources = bld.path.ant_glob([
+		'opus/src/*.c',
+		'opus/celt/*.c',
+		'opus/silk/*.c',
+		'opus/silk/float/*.c'
+	])
+	includes = ['opus/include/', 'opus/celt/', 'opus/silk/', 'opus/silk/float/']
+	defines = ['USE_ALLOCA', 'OPUS_BUILD', 'FLOAT_APPROX', 'PACKAGE_VERSION="1.3.1"']
+
+	bld.stlib(
+		source = sources,
+		target = 'opus',
+		features = 'c',
+		includes = includes,
+		defines = defines,
+		subsystem = bld.env.MSVC_SUBSYSTEM,
+		export_includes = ['opus/include/']
+	)