build: don't force SSE on i386

--- src/ext/PBA/CMakeLists.txt.orig	2017-06-15 14:32:01 UTC
+++ src/ext/PBA/CMakeLists.txt
@@ -1,5 +1,5 @@
 if(NOT IS_MSVC)
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fPIC -O3 -pthread -march=core2 -mfpmath=sse -Wno-c++11-narrowing")
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-c++11-narrowing")
 endif()
 
 if(CUDA_ENABLED)
--- src/ext/PBA/SparseBundleCPU.cpp.orig	2017-06-15 14:32:01 UTC
+++ src/ext/PBA/SparseBundleCPU.cpp
@@ -52,15 +52,16 @@ using std::max;
 #if defined(_M_ARM) && _M_ARM >= 7 && !defined(DISABLE_CPU_NEON)
 #include <arm_neon.h>
 #define CPUPBA_USE_NEON
-#elif defined(__ARM_NEON__) && !defined(DISABLE_CPU_NEON)
+#elif defined(__ARM_NEON) && !defined(DISABLE_CPU_NEON)
 #include <arm_neon.h>
 #define CPUPBA_USE_NEON
 #endif
-#elif defined(CPUPBA_USE_AVX)  // Using AVX
+#elif defined(__AVX__) && !defined(DISABLE_CPU_AVX)  // Using AVX
 #include <immintrin.h>
+#define CPUPBA_USE_AVX
 #undef CPUPBA_USE_SSE
 #undef POINT_DATA_ALIGN4
-#elif !defined(DISABLE_CPU_SSE)  // Using SSE
+#elif defined(__SSE2__) && !defined(DISABLE_CPU_SSE)  // Using SSE
 #define CPUPBA_USE_SSE
 #include <xmmintrin.h>
 #include <emmintrin.h>
