- make ARM compiler flags optional, detect based on ${ZDOOM_TARGET_AR…

…CH}, do not activate on Apple build systems

src/CMakeLists.txt

@@ -319,7 +319,11 @@ if( ZD_CMAKE_COMPILER_IS_GNUCXX_COMPATIBLE )
 	set( CMAKE_CXX_FLAGS "-Wall -Wextra -Wno-unused -Wno-unused-parameter -Wno-missing-field-initializers -ffp-contract=off ${CMAKE_CXX_FLAGS}" )
 
 	# ARM processors (Raspberry Pi, et al) - enable ARM NEON support.
-	if(${CMAKE_SYSTEM_PROCESSOR} MATCHES "arm")
+	if(${ZDOOM_TARGET_ARCH} MATCHES "arm" AND NOT APPLE)
+		set (USE_LINUX_ARM 1 CACHE BOOL "Compile for ARM - Linux")
+	endif ()
+
+	if (USE_LINUX_ARM)
 		set (USE_ARMV8 0 CACHE BOOL "Use ARMv8 instructions - Raspberry Pi 3")
 		if (USE_ARMV8)
 			set( CMAKE_CXX_FLAGS "-mcpu=cortex-a53 -mfpu=neon-fp-armv8 -mtune=cortex-a53 -mhard-float -DNO_SSE ${CMAKE_CXX_FLAGS}" )