Add fuzzing language correctly during compile step. (#3837)

infra/gcb/build_lib.py

@@ -184,7 +184,6 @@ def project_image_steps(name, image, language):
           '.',
       ],
       'dir': 'oss-fuzz/projects/' + name,
-      'env': ['FUZZING_LANGUAGE=%s' % language],
   }, {
       'name':
           image,

infra/gcb/build_project.py

@@ -161,6 +161,7 @@ def get_build_steps(project_dir):
         env.append('OUT=' + out)
         env.append('MSAN_LIBS_PATH=/workspace/msan')
         env.append('ARCHITECTURE=' + architecture)
+        env.append('FUZZING_LANGUAGE=' + language)
 
         workdir = workdir_from_dockerfile(dockerfile_path)
         if not workdir: