Update leveldb-1.4.patch to support PowerPC LE platform.

Review: https://reviews.apache.org/r/44382/

3rdparty/leveldb-1.4.patch

@@ -28,3 +28,30 @@ index b71bf02..864e5fb 100755
  fi
 
  PLATFORM_CCFLAGS="$PLATFORM_CCFLAGS $COMMON_FLAGS"
+diff --git a/port/atomic_pointer.h b/port/atomic_pointer.h
+index 35ae550..b4769b3 100644
+--- a/port/atomic_pointer.h
++++ b/port/atomic_pointer.h
+@@ -36,6 +36,8 @@
+ #define ARCH_CPU_X86_FAMILY 1
+ #elif defined(__ARMEL__)
+ #define ARCH_CPU_ARM_FAMILY 1
++#elif defined(__ppc__) || defined(__powerpc__) || defined(__powerpc64__)
++#define ARCH_CPU_PPC_FAMILY 1
+ #endif
+
+ namespace leveldb {
+@@ -83,6 +85,13 @@ inline void MemoryBarrier() {
+ }
+ #define LEVELDB_HAVE_MEMORY_BARRIER
+
++// PPC
++#elif defined(ARCH_CPU_PPC_FAMILY) && defined(__GNUC__)
++inline void MemoryBarrier() {
++  asm volatile("lwsync" : : : "memory");
++}
++#define LEVELDB_HAVE_MEMORY_BARRIER
++
+ #endif
+
+ // AtomicPointer built using platform-specific MemoryBarrier()