zephyr: Update GOOGLE_RTC_AUDIO_PROCESSING

Unbreak the Zephyr build when this is enabled, and add the needed bits
to produce a working executable.

This is mostly just a recapitulation of the existing integration,
which means that it's manually pulling in bits from the Cadence
toolchain it needs.  Really this is nothing more than a C++ library
and it shouldn't have to do anything other than enable CONFIG_CPP=y in
the build.  But the upstream Zephyr C++ toolchain integration for
xcc/xt-clang isn't present yet.

Signed-off-by: Andy Ross <andyross@google.com>

Author: andyross

zephyr/CMakeLists.txt

@@ -837,10 +837,6 @@ zephyr_library_sources_ifdef(CONFIG_COMP_MULTIBAND_DRC
 	${SOF_AUDIO_PATH}/multiband_drc/multiband_drc_generic.c
 )
 
-zephyr_library_sources_ifdef(CONFIG_COMP_GOOGLE_RTC_AUDIO_PROCESSING
-	${SOF_AUDIO_PATH}/google_rtc_audio_processing.c
-)
-
 zephyr_library_sources_ifdef(CONFIG_COMP_IGO_NR
 	${SOF_AUDIO_PATH}/igo_nr/igo_nr.c
 )
@@ -916,6 +912,29 @@ zephyr_library_sources_ifdef(CONFIG_DW_DMA
 	${SOF_DRIVERS_PATH}/dw/dma.c
 )
 
+if(CONFIG_COMP_GOOGLE_RTC_AUDIO_PROCESSING)
+	zephyr_library_sources(${SOF_AUDIO_PATH}/google/google_rtc_audio_processing.c)
+	zephyr_library_sources_ifdef(CONFIG_GOOGLE_RTC_AUDIO_PROCESSING_MOCK
+		${SOF_AUDIO_PATH}/google/google_rtc_audio_processing_mock.c)
+	zephyr_include_directories(../third_party/include)
+	target_link_directories(SOF INTERFACE ../third_party/lib)
+	target_link_libraries(SOF INTERFACE google_rtc_audio_processing)
+
+	# This isn't quite right, Zephyr should be providing a C++
+	# linkage environment for the toolchain, but the xcc/xt-clang
+	# integration isn't yet.  Note we need to specify libc/libm
+	# because the Cadence C++ standard library is tightly coupled
+	# to their own libc (which is just a newlib).  And I have NO
+	# idea why libgcc isn't on the link currently, that's a Zephyr
+	# mistake and I guess I'm surprised nothing else has broken.
+	# Needs to be cleaned up Zephyr-side.
+	target_link_libraries(SOF INTERFACE c++)
+	target_link_libraries(SOF INTERFACE c++abi)
+	target_link_libraries(SOF INTERFACE m)
+	target_link_libraries(SOF INTERFACE c)
+	target_link_libraries(SOF INTERFACE gcc)
+endif()
+
 zephyr_library_link_libraries(SOF)
 target_link_libraries(SOF INTERFACE zephyr_interface)