contrib: salsa: add SALSA-lib 0.2.0

This provides for audio input/output on embedded Linux.

contrib/src/salsa/rules.mak

+# SALSA-lib
+
+SALSA_URL = https://github.com/tiwai/salsa-lib.git
+SALSA_TAG = v0.2.0
+SALSA_HASH = a3e5accc0b34ddc59fea2342f1ab1f8be179cf9d
+
+SALSACONF = \
+	--enable-chmap \
+	--enable-conf \
+	--enable-float \
+	--enable-output \
+	--enable-pcm \
+	--disable-4bit \
+	--disable-mixer \
+	--disable-user-elem
+
+$(TARBALLS)/salsa-lib-$(SALSA_TAG).tar.xz:
+	$(call download_git,$(SALSA_URL),$(SALSA_TAG),$(SALSA_HASH))
+
+.sum-salsa: $(TARBALLS)/salsa-lib-$(SALSA_TAG).tar.xz
+	$(call check_githash,$(SALSA_HASH))
+	touch $@
+
+salsa-lib: salsa-lib-$(SALSA_TAG).tar.xz .sum-salsa
+	$(UNPACK)
+	$(MOVE)
+
+.salsa: salsa-lib
+	$(RECONF)
+	cd $< && ./configure $(HOSTVARS) $(HOSTCONF) $(SALSACONF)
+	cd $< && $(MAKE) install
+	touch $@
+
+# ALSA placeholder
+
+PKGS_ALL += alsa
+
+ifdef HAVE_LINUX
+ifndef HAVE_ANDROID
+PKGS += alsa
+endif
+endif
+ifeq ($(call need_pkg, "alsa >= 1.0.24"),)
+PKGS_FOUND += alsa
+endif
+
+DEPS_alsa = salsa $(DEPS_salsa)
+
+.sum-alsa: .sum-salsa
+	touch $@
+
+.alsa: .sum-alsa
+	touch $@