Make Platform.executable return a fully qualified path the the executable

runtime/bin/platform_linux.cc

Index: runtime/bin/platform_linux.cc
diff --git a/runtime/bin/platform_linux.cc b/runtime/bin/platform_linux.cc
index f6dfaa17137ee137fce3d3c89f16c13cda733099..8469a21cb22b7a56719da87cc5387fbbb3125bee 100644
--- a/runtime/bin/platform_linux.cc
+++ b/runtime/bin/platform_linux.cc
@@ -5,6 +5,7 @@
 #include "platform/globals.h"
 #if defined(TARGET_OS_LINUX)
 
+#include "bin/file.h"
 #include "bin/platform.h"
 
 #include <signal.h>  // NOLINT
@@ -71,6 +72,11 @@ void Platform::FreeEnvironment(char** env, intptr_t count) {
   delete[] env;
 }
 
+
+char* Platform::ResolveExecutablePath() {
+  return File::LinkTarget("/proc/self/exe");
+}
+
 }  // namespace bin
 }  // namespace dart