dsp(build): honor single-arch CMAKE_OSX_ARCHITECTURES for SIMD selection

Author: arancormonk

src/dsp/CMakeLists.txt

@@ -22,8 +22,16 @@ target_sources(dsd-neo_dsp PRIVATE
 	  sync_calibration.c
 )
 
+set(_dsd_neo_dsp_target_arch "${CMAKE_SYSTEM_PROCESSOR}")
+if(APPLE AND CMAKE_OSX_ARCHITECTURES)
+  list(LENGTH CMAKE_OSX_ARCHITECTURES _dsd_neo_osx_arch_count)
+  if(_dsd_neo_osx_arch_count EQUAL 1)
+    list(GET CMAKE_OSX_ARCHITECTURES 0 _dsd_neo_dsp_target_arch)
+  endif()
+endif()
+
 # x86-64 SIMD sources with arch-specific flags
-if(CMAKE_SYSTEM_PROCESSOR MATCHES "x86_64|AMD64|amd64")
+if(_dsd_neo_dsp_target_arch MATCHES "x86_64|AMD64|amd64")
   target_sources(dsd-neo_dsp PRIVATE simd_fir_sse2.cpp)
   target_sources(dsd-neo_dsp PRIVATE simd_widen_sse2.cpp)
   # Explicit SSE2 flag for clarity and cross-compilation safety
@@ -56,7 +64,7 @@ if(CMAKE_SYSTEM_PROCESSOR MATCHES "x86_64|AMD64|amd64")
 endif()
 
 # ARM64 NEON (always available on AArch64)
-if(CMAKE_SYSTEM_PROCESSOR MATCHES "aarch64|arm64|ARM64")
+if(_dsd_neo_dsp_target_arch MATCHES "aarch64|arm64|ARM64")
   target_sources(dsd-neo_dsp PRIVATE simd_fir_neon.cpp)
   target_sources(dsd-neo_dsp PRIVATE simd_widen_neon.cpp)
 endif()