调整gperftools中Heap Profiler输出字符串缓冲区大小到1<<22，并升级gperftools.

* heap profiler工具中定义的Heap文件输出缓冲区过小（1<<20），当使用内存较多时无法正确输出Heap文件。通过Patch的方式调整。
  * 升级gperftools到最新稳定版本2.8。

vendor/CMakeLists.txt

@@ -101,7 +101,7 @@ ExternalProject_Add(ratelimiter PREFIX ratelimiter
 		CONFIGURE_COMMAND ""
 		BUILD_COMMAND make
         BUILD_IN_SOURCE 1)
-		
+
 ExternalProject_Get_Property(ratelimiter INSTALL_DIR)
 file(MAKE_DIRECTORY ${INSTALL_DIR}/include)
 
@@ -334,8 +334,9 @@ target_link_libraries(brotlienc-static INTERFACE brotlicommon-static)
 ### gperftools
 ExternalProject_Add(gperftools
         PREFIX gperftools
-        URL ${CMAKE_CURRENT_SOURCE_DIR}/gperftools-2.7.tar.gz
+        URL ${CMAKE_CURRENT_SOURCE_DIR}/gperftools-2.8.tar.gz
-        URL_MD5 c6a852a817e9160c79bdb2d3101b4601
+        URL_MD5 ea61ad1e886f53e4069873ce52cae7df
+        PATCH_COMMAND patch -p1 < ${CMAKE_CURRENT_LIST_DIR}/patch/gperftools-fix_too_small_heap_profile_buffer_size.patch
         CONFIGURE_COMMAND ./configure --prefix=<INSTALL_DIR> --disable-shared
         BUILD_IN_SOURCE 1)
 

vendor/patch/gperftools-fix_too_small_heap_profile_buffer_size.patch

@@ -0,0 +1,13 @@
+diff --git a/src/heap-profiler.cc b/src/heap-profiler.cc
+index 33a25ac..4d750bb 100644
+--- a/src/heap-profiler.cc
++++ b/src/heap-profiler.cc
+@@ -151,7 +151,7 @@ static void ProfilerFree(void* p) {
+ }
+ 
+ // We use buffers of this size in DoGetHeapProfile.
+-static const int kProfileBufferSize = 1 << 20;
++static const int kProfileBufferSize = 1 << 22;
+ 
+ // This is a last-ditch buffer we use in DumpProfileLocked in case we
+ // can't allocate more memory from ProfilerMalloc.  We expect this