pulseaudio: fix build error on toolchains without C++ support

The optional webrtc echo canceller is written in C++, causing auto* to want
to link module-echo-cancel.so with CXX even if webrtc ISN'T used.
If we don't have C++ support enabled in BR, CXX will point to /bin/false,
which makes configure think we aren't able to create C++ .so files
(arguable true), breaking the build when it tries to install the .so
workaround it by patching up the libtool invocations to use C mode instead.

Fixes http://autobuild.buildroot.net/results/114e5bf0086f2394b36f17a70cb54b357a72413c

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/multimedia/pulseaudio/pulseaudio.mk

@@ -32,6 +32,21 @@ PULSEAUDIO_DEPENDENCIES = \
 	$(if $(BR2_PACKAGE_WEBRTC_AUDIO_PROCESSING),webrtc-audio-processing) \
 	$(if $(BR2_PACKAGE_SYSTEMD),systemd)
 
+ifneq ($(BR2_INSTALL_LIBSTDCPP),y)
+# The optional webrtc echo canceller is written in C++, causing auto* to want
+# to link module-echo-cancel.so with CXX even if webrtc ISN'T used.
+# If we don't have C++ support enabled in BR, CXX will point to /bin/false,
+# which makes configure think we aren't able to create C++ .so files
+# (arguable true), breaking the build when it tries to install the .so
+# workaround it by patching up the libtool invocations to use C mode instead
+define PULSEAUDIO_FORCE_CC
+	$(SED) 's/--tag=CXX/--tag=CC/g' -e 's/(CXXLD)/(CCLD)/g' \
+		$(@D)/src/Makefile.in
+endef
+
+PULSEAUDIO_POST_PATCH_HOOKS += PULSEAUDIO_FORCE_CC
+endif
+
 # pulseaudio alsa backend needs pcm/mixer apis
 ifneq ($(BR2_PACKAGE_ALSA_LIB_PCM)$(BR2_PACKAGE_ALSA_LIB_MIXER),yy)
 PULSEAUDIO_CONF_OPT += --disable-alsa