[fuchsia] Uprev test-scripts with FUCHSIA_READELF env (#166929)

Copied from https://github.com/flutter/flutter/pull/166901 with the
essential fix to make it work.

Bug: b/407890258, b/338009514

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DEPS

@@ -211,7 +211,7 @@ vars = {
   # The version / instance id of the cipd:chromium/fuchsia/test-scripts which
   # will be used altogether with fuchsia-sdk to setup the build / test
   # environment.
-  'fuchsia_test_scripts_version': 'FZdRtNwH7jmADecj60ClOK69AHHnfTvvuwKLUgY0_AoC',
+  'fuchsia_test_scripts_version': 'mApUsju36efRytN4WFdopPYMfYgAI8ODzTmYq3zNEqsC',
 
   # The version / instance id of the cipd:chromium/fuchsia/gn-sdk which will be
   # used altogether with fuchsia-sdk to generate gn based build rules.

engine/src/flutter/tools/fuchsia/with_envs.py

@@ -18,7 +18,7 @@ def Main():
     Executes the test-scripts with required environment variables. It acts like
     /usr/bin/env, but provides some extra functionality to dynamically set up
     the environment variables.
-    """
+  """
   # Ensures the signals can be correctly forwarded to the subprocesses.
   catch_sigterm()
 
@@ -32,6 +32,9 @@ def Main():
   os.environ['FUCHSIA_GN_SDK_ROOT'] = os.path.join(
       os.environ['SRC_ROOT'], 'flutter/tools/fuchsia/gn-sdk/src'
   )
+  os.environ['FUCHSIA_READELF'] = os.path.join(
+      os.environ['SRC_ROOT'], 'flutter/buildtools/linux-x64/clang/bin/llvm-readelf'
+  )
 
   if os.getenv('DOWNLOAD_FUCHSIA_SDK') == 'True':
     sdk_path = os.environ['FUCHSIA_SDK_PATH']