cmake: add FindPortAudio script

PortAudio only added a config a few weeks ago which means most package managers don't have it. I don't know if there's a way to use the config without having our own find script, but we'll see.

CMakeLists.txt

@@ -122,7 +122,8 @@ list(APPEND OLIVE_LIBRARIES
 
 # Link PortAudio
 find_package(PortAudio REQUIRED)
-list(APPEND OLIVE_LIBRARIES PortAudio)
+list(APPEND OLIVE_INCLUDE_DIRS ${PORTAUDIO_INCLUDE_DIRS})
+list(APPEND OLIVE_LIBRARIES ${PORTAUDIO_LIBRARIES})
 
 # Optional: Link OpenTimelineIO
 find_package(OpenTimelineIO)

cmake/FindPortAudio.cmake

@@ -0,0 +1,32 @@
+# - Find PortAudio includes and libraries
+#
+#   PORTAUDIO_FOUND        - True if PORTAUDIO_INCLUDE_DIR & PORTAUDIO_LIBRARY
+#                            are found
+#   PORTAUDIO_LIBRARIES    - Set when PORTAUDIO_LIBRARY is found
+#   PORTAUDIO_INCLUDE_DIRS - Set when PORTAUDIO_INCLUDE_DIR is found
+#
+#   PORTAUDIO_INCLUDE_DIR - where to find portaudio.h, etc.
+#   PORTAUDIO_LIBRARY     - the portaudio library
+#
+
+find_path(PORTAUDIO_INCLUDE_DIR
+          NAMES portaudio.h
+          DOC "The PortAudio include directory"
+)
+
+find_library(PORTAUDIO_LIBRARY
+             NAMES portaudio
+             DOC "The PortAudio library"
+)
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(PortAudio
+    REQUIRED_VARS PORTAUDIO_LIBRARY PORTAUDIO_INCLUDE_DIR
+)
+
+if(PORTAUDIO_FOUND)
+    set(PORTAUDIO_LIBRARIES ${PORTAUDIO_LIBRARY})
+    set(PORTAUDIO_INCLUDE_DIRS ${PORTAUDIO_INCLUDE_DIR})
+endif()
+
+mark_as_advanced(PORTAUDIO_INCLUDE_DIR PORTAUDIO_LIBRARY)