Add fallback for cache line size detection

- Provide default cache line size for systems without _SC_LEVEL1_DCACHE_LINESIZE
- Set default to 64 bytes, which is common on x86_64 architectures
- Improve portability of cache line size detection

malign_buffer.cc

@@ -127,7 +127,12 @@ void MalignBuffer::InitializeMemoryForSanitizer(char *addr, size_t size) {
 }
 
 const size_t MalignBuffer::kPageSize = sysconf(_SC_PAGESIZE);
+#ifdef _SC_LEVEL1_DCACHE_LINESIZE
 const size_t MalignBuffer::kCacheLineSize = sysconf(_SC_LEVEL1_DCACHE_LINESIZE);
+#else
+// Default to 64 bytes which is common on x86_64
+const size_t MalignBuffer::kCacheLineSize = 64;
+#endif
 
 std::string MalignBuffer::ToString(CopyMethod m) {
   switch (m) {