Implemented basic heap memory allocation tracking in MallocHooks using hooks registered with tcmall…

runtime/bin/BUILD.gn

Index: runtime/bin/BUILD.gn
diff --git a/runtime/bin/BUILD.gn b/runtime/bin/BUILD.gn
index ee6119a13de2e48967575ecd44f52ec8428a17fd..67608c50c6042bc536bc60ed89452792cd067d54 100644
--- a/runtime/bin/BUILD.gn
+++ b/runtime/bin/BUILD.gn
@@ -297,6 +297,10 @@ executable("gen_snapshot") {
 
   include_dirs = [ ".." ]
 
+  if (dart_use_tcmalloc) {
+    deps += [ "//third_party/tcmalloc" ]
+  }
+
   if (is_mac) {
     libs = [
       "CoreFoundation.framework",
@@ -574,7 +578,6 @@ template("dart_executable") {
 
     if (dart_use_tcmalloc) {
       deps += [ "//third_party/tcmalloc" ]
-      defines += [ "DART_USE_TCMALLOC" ]
     }
 
     sources = [