Add more linker debug.

- Show which executable is being linked, which linker config file is
  being read, and which section in it is being used with, enabled on
  $LD_DEBUG>=1.

- Show more info to follow the dlopen() process, enabled with "dlopen"
  in the debug.ld.xxx property.

Test: Flash, boot, and look at logcat after "adb shell setprop debug.ld.all dlopen"
Bug: 120430775
Change-Id: I5441c8ced26ec0e2f04620c3d2a1ae860b792154
diff --git a/linker/linker_main.cpp b/linker/linker_main.cpp
index 9de7f51..6c762a9 100644
--- a/linker/linker_main.cpp
+++ b/linker/linker_main.cpp
@@ -353,6 +353,8 @@
   // a C-style string to last until the program exits.
   static std::string exe_path = exe_info.path;
 
+  INFO("[ Linking executable \"%s\" ]", exe_path.c_str());
+
   // Initialize the main exe's soinfo.
   soinfo* si = soinfo_alloc(&g_default_namespace,
                             exe_path.c_str(), &exe_info.file_stat,