Fix linux_clang default try builder to only compile and not run tests.

PRESUBMIT.py

Index: PRESUBMIT.py
diff --git a/PRESUBMIT.py b/PRESUBMIT.py
index 87f089419eb057c1c858a64a54833db12eb5801a..0bb8ac8b69e43ab0407404e3851f651142808ccb 100644
--- a/PRESUBMIT.py
+++ b/PRESUBMIT.py
@@ -328,10 +328,7 @@ def GetPreferredTrySlaves(project, change):
   only_objc_files = all(f.endswith(('.mm', '.m')) for f in affected_files)
   if only_objc_files:
     return ['mac_rel']
-  preferred = ['win_rel', 'linux_rel', 'mac_rel']
-  preferred = ['win_rel', 'linux_rel', 'mac_rel', 'linux_clang']
-  if any(f.endswith(('.h', '.cc', '.cpp', '.cxx')) for f in affected_files):
-    preferred.append('linux_clang')
+  preferred = ['win_rel', 'linux_rel', 'mac_rel', 'linux_clang:compile']
   aura_re = '_aura[^/]*[.][^/]*'
   if any(re.search(aura_re, f) for f in affected_files):
     preferred.append('linux_chromeos')