Only emit SIMD compiler flags on x86-based platforms

Enabling the SSE4.2 or AVX SIMD flags on non-x86 based platforms will
result in a compilation error stating that the -msse4.2 and -mavx flags
cannot be found. This patch causes the flags to only be emitted on x86-based
platforms.

Signed-off-by: jmather-sesi <54645798+jmather-sesi@users.noreply.github.com>

CMakeLists.txt

@@ -386,12 +386,16 @@ endif()
 # Configure SIMD. AVX implies SSE 4.2.
 
 if(OPENVDB_SIMD STREQUAL "AVX")
-  add_compile_options("$<$<COMPILE_LANGUAGE:CXX>:-mavx>")
-  add_compile_options("$<$<COMPILE_LANGUAGE:CXX>:-msse4.2>")
+  if (CMAKE_SYSTEM_PROCESSOR MATCHES "(x86)|(X86)|(amd64)|(AMD64)")
+    add_compile_options("$<$<COMPILE_LANGUAGE:CXX>:-mavx>")
+    add_compile_options("$<$<COMPILE_LANGUAGE:CXX>:-msse4.2>")
+  endif()
   add_compile_definitions("$<$<COMPILE_LANGUAGE:CXX>:OPENVDB_USE_AVX>")
   add_compile_definitions("$<$<COMPILE_LANGUAGE:CXX>:OPENVDB_USE_SSE42>")
 elseif(OPENVDB_SIMD STREQUAL "SSE42")
-  add_compile_options("$<$<COMPILE_LANGUAGE:CXX>:-msse4.2>")
+  if (CMAKE_SYSTEM_PROCESSOR MATCHES "(x86)|(X86)|(amd64)|(AMD64)")
+    add_compile_options("$<$<COMPILE_LANGUAGE:CXX>:-msse4.2>")
+  endif()
   add_compile_definitions("$<$<COMPILE_LANGUAGE:CXX>:OPENVDB_USE_SSE42>")
 endif()