Fuchsia: resolve executable name, fetch environment vars

runtime/bin/file_fuchsia.cc

Index: runtime/bin/file_fuchsia.cc
diff --git a/runtime/bin/file_fuchsia.cc b/runtime/bin/file_fuchsia.cc
index bda61138c711fd3e395635b32e79a63859e51e6e..130d0310c3833f2790dc2cf1c1b73801c356bb96 100644
--- a/runtime/bin/file_fuchsia.cc
+++ b/runtime/bin/file_fuchsia.cc
@@ -353,6 +353,8 @@ bool File::IsAbsolutePath(const char* pathname) {
 
 
 const char* File::GetCanonicalPath(const char* pathname) {
+  // TODO(MG-425): realpath() is not implemented.
+#if 0
   char* abs_path = NULL;
   if (pathname != NULL) {
     char* resolved_path = DartUtils::ScopedCString(PATH_MAX + 1);
@@ -364,6 +366,9 @@ const char* File::GetCanonicalPath(const char* pathname) {
     ASSERT((abs_path == NULL) || (abs_path == resolved_path));
   }
   return abs_path;
+#else
+  return pathname;
+#endif
 }