Ignore missing library dependencies in CMake

Signed-off-by: Marcin Serwin <marcin@serwin.dev>

CMakeLists.txt

@@ -616,10 +616,13 @@ set(LINKED_LIBS)
 if(MINIAUDIO_NO_RUNTIME_LINKING)
     is_backend_enabled(PULSEAUDIO)
     if (PULSEAUDIO_ENABLED)
-        find_package(PulseAudio REQUIRED)
-        target_link_libraries(miniaudio PRIVATE ${PULSEAUDIO_LIBRARY})
-        target_include_directories(miniaudio SYSTEM PRIVATE ${PULSEAUDIO_INCLUDE_DIR})
-        list(APPEND LINKED_LIBS libpulse)
+        find_package(PulseAudio)
+
+        if (PulseAudio_FOUND)
+            target_link_libraries(miniaudio PRIVATE ${PULSEAUDIO_LIBRARY})
+            target_include_directories(miniaudio SYSTEM PRIVATE ${PULSEAUDIO_INCLUDE_DIR})
+            list(APPEND LINKED_LIBS libpulse)
+        endif()
     endif()
 
     is_backend_enabled(ALSA)
@@ -634,14 +637,17 @@ if(MINIAUDIO_NO_RUNTIME_LINKING)
             NAMES asound
             HINTS ${PC_ALSA_LIBRARY_DIRS}
         )
-        find_path(ALSA_INCLUDE_DIR
-            NAMES alsa/asoundlib.h
-            HINTS ${PC_ALSA_INCLUDE_DIRS}
-        )
 
-        target_link_libraries(miniaudio PRIVATE ${ALSA_LIBRARY})
-        target_include_directories(miniaudio PRIVATE ${ALSA_INCLUDE_DIR})
-        list(APPEND LINKED_LIBS alsa)
+        if (ALSA_LIBRARY)
+            find_path(ALSA_INCLUDE_DIR
+                NAMES alsa/asoundlib.h
+                HINTS ${PC_ALSA_INCLUDE_DIRS}
+            )
+
+            target_link_libraries(miniaudio PRIVATE ${ALSA_LIBRARY})
+            target_include_directories(miniaudio PRIVATE ${ALSA_INCLUDE_DIR})
+            list(APPEND LINKED_LIBS alsa)
+        endif()
     endif()
 
     is_backend_enabled(SNDIO)
@@ -656,8 +662,11 @@ if(MINIAUDIO_NO_RUNTIME_LINKING)
             NAMES sndio
             HINTS ${PC_SNDIO_LIBRARY_DIRS}
         )
-        target_link_libraries(miniaudio PRIVATE ${SNDIO_LIBRARY})
-        list(APPEND LINKED_LIBS sndio)
+
+        if (SNDIO_LIBRARY)
+            target_link_libraries(miniaudio PRIVATE ${SNDIO_LIBRARY})
+            list(APPEND LINKED_LIBS sndio)
+        endif()
     endif()
 
     is_backend_enabled(JACK)
@@ -673,14 +682,16 @@ if(MINIAUDIO_NO_RUNTIME_LINKING)
             HINTS ${PC_JACK_LIBRARY_DIRS}
         )
 
-        find_path(JACK_INCLUDE_DIR
-            NAMES jack/jack.h
-            HINTS ${PC_JACK_INCLUDE_DIRS}
-        )
+        if (JACK_LIBRARY)
+            find_path(JACK_INCLUDE_DIR
+                NAMES jack/jack.h
+                HINTS ${PC_JACK_INCLUDE_DIRS}
+            )
 
-        target_link_libraries(miniaudio PRIVATE ${JACK_LIBRARY})
-        target_include_directories(miniaudio PRIVATE ${JACK_INCLUDE_DIR})
-        list(APPEND LINKED_LIBS jack)
+            target_link_libraries(miniaudio PRIVATE ${JACK_LIBRARY})
+            target_include_directories(miniaudio PRIVATE ${JACK_INCLUDE_DIR})
+            list(APPEND LINKED_LIBS jack)
+        endif()
     endif()
 endif()