CMake: build PortAudio as static library

Due to issues raised in #4255.

CMakeLists.txt

@@ -559,9 +559,11 @@ if(NOT ANDROID)
 	endif()
 	if(SYSTEM_PORTAUDIO AND NOT APPLE)
 		message("Using shared PortAudio for mic support")
+		set(PORTAUDIO_LIBRARIES portaudio)
 	else()
 		message("Using static PortAudio from Externals for mic support")
 		add_subdirectory(Externals/portaudio)
+		set(PORTAUDIO_LIBRARIES portaudio_static)
 	endif()
 endif()
 

Source/Core/Core/CMakeLists.txt

@@ -274,7 +274,7 @@ if(HIDAPI_FOUND)
 endif(HIDAPI_FOUND)
 
 if(PORTAUDIO_FOUND)
-	set(LIBS ${LIBS} portaudio)
+	set(LIBS ${LIBS} ${PORTAUDIO_LIBRARIES})
 endif(PORTAUDIO_FOUND)
 
 if(OPROFILE_FOUND)