Only set Core Audio session category for iOS targets

Fixes a crash in the latest UAT desktop editor(s) on macOS by targeting setting iOS session category to mixing only for iOS / iPadOS / Catalyst targets. The desktop editor is _not_ any of these targets, so the code changes are not compiled.

See [here](https://github.com/rive-app/rive/pull/7555/files#r1680306818) for more discussion.

Diffs=
6c5c79b75 Only set Core Audio session category for iOS targets (#7624)

Co-authored-by: David Skuza <david@rive.app>

.rive_head

diff --git a/.rive_head b/.rive_head
index b46f69f..fb5018f 100644
--- a/.rive_head
+++ b/.rive_head
@@ -1 +1 @@
-8e1be1223161ced9cfb80c0ec3671ffd25ee5cfb
+6c5c79b751c50fa4393fb0e44624635861bc3f3b

src/audio/audio_engine.cpp

diff --git a/src/audio/audio_engine.cpp b/src/audio/audio_engine.cpp
index da48702..0bdd9f9 100644
--- a/src/audio/audio_engine.cpp
+++ b/src/audio/audio_engine.cpp
@@ -166,7 +166,8 @@
 // I _think_ MA_NO_DEVICE_IO is defined when building for Unity; otherwise, it seems to pass
 // "standard" building When defined, pContext is unavailable, which causes build errors when
 // building Unity for iOS. - David
-#if defined(MA_HAS_COREAUDIO) && !defined(MA_NO_DEVICE_IO)
+#if (TARGET_IPHONE_SIMULATOR || TARGET_OS_MACCATALYST || TARGET_OS_IPHONE) &&                      \
+    !defined(MA_NO_DEVICE_IO)
     // Used for configuration only, and isn't referenced past the usage of ma_context_init; thus,
     // can be locally scoped. Uses the "logical" defaults from miniaudio, and updates only what we
     // need. This should automatically set available backends in priority order based on the target
@@ -190,7 +191,8 @@
     engineConfig.channels = numChannels;
     engineConfig.sampleRate = sampleRate;
 
-#if defined(MA_HAS_COREAUDIO) && !defined(MA_NO_DEVICE_IO)
+#if (TARGET_IPHONE_SIMULATOR || TARGET_OS_MACCATALYST || TARGET_OS_IPHONE) &&                      \
+    !defined(MA_NO_DEVICE_IO)
     if (context != nullptr)
     {
         engineConfig.pContext = context;
@@ -205,7 +207,8 @@
 
     if (ma_engine_init(&engineConfig, engine) != MA_SUCCESS)
     {
-#if defined(MA_HAS_COREAUDIO) && !defined(MA_NO_DEVICE_IO)
+#if (TARGET_IPHONE_SIMULATOR || TARGET_OS_MACCATALYST || TARGET_OS_IPHONE) &&                      \
+    !defined(MA_NO_DEVICE_IO)
         if (context != nullptr)
         {
             ma_context_uninit(context);
@@ -405,7 +408,8 @@
     }
     m_completedSounds.clear();
 
-#if defined(MA_HAS_COREAUDIO) && !defined(MA_NO_DEVICE_IO)
+#if (TARGET_IPHONE_SIMULATOR || TARGET_OS_MACCATALYST || TARGET_OS_IPHONE) &&                      \
+    !defined(MA_NO_DEVICE_IO)
     // m_context is only set when Core Audio is available
     if (m_context != nullptr)
     {