[x86] Disable AVX unless the operating system explicitly claims to support it.

src/base/cpu.cc

Index: src/base/cpu.cc
diff --git a/src/base/cpu.cc b/src/base/cpu.cc
index b5786a57f35f3d256e8fb20035a7cff99a930868..fa212e0e045b572078f9782cbbc49020d00f4cb7 100644
--- a/src/base/cpu.cc
+++ b/src/base/cpu.cc
@@ -316,6 +316,7 @@ CPU::CPU()
       has_sse41_(false),
       has_sse42_(false),
       is_atom_(false),
+      has_osxsave_(false),
       has_avx_(false),
       has_fma3_(false),
       has_idiva_(false),
@@ -364,8 +365,9 @@ CPU::CPU()
     has_ssse3_ = (cpu_info[2] & 0x00000200) != 0;
     has_sse41_ = (cpu_info[2] & 0x00080000) != 0;
     has_sse42_ = (cpu_info[2] & 0x00100000) != 0;
+    has_osxsave_ = (cpu_info[2] & 0x08000000) != 0;
     has_avx_ = (cpu_info[2] & 0x10000000) != 0;
-    if (has_avx_) has_fma3_ = (cpu_info[2] & 0x00001000) != 0;
+    has_fma3_ = (cpu_info[2] & 0x00001000) != 0;
 
     if (family_ == 0x6) {
       switch (model_) {