Trees are closed because of this issue: https://treeherder.mozilla.org/#/jobs?repo=mozilla-central&filter-resultStatus=testfailed&filter-resultStatus=busted&filter-resultStatus=exception&filter-resultStatus=success&filter-classifiedState=unclassified&filter-searchStr=cross&selectedJob=189254788 Failure log: https://treeherder.mozilla.org/logviewer.html#?job_id=189254201&repo=mozilla-central&lineNumber=914 [task 2018-07-20T21:49:53.774Z] 21:49:53 INFO - checking for 64-bit OS... yes [task 2018-07-20T21:49:53.774Z] 21:49:53 INFO - checking bindgen cflags... [u'-target', u'x86_64-apple-darwin11', u'-B', u'/builds/worker/workspace/build/src/cctools/bin', u'-isysroot', u'/builds/worker/workspace/build/src/MacOSX10.11.sdk'] [task 2018-07-20T21:49:53.781Z] 21:49:53 INFO - checking for linker... [task 2018-07-20T21:49:53.781Z] 21:49:53 INFO - DEBUG: Executing: `/builds/worker/workspace/build/src/clang/bin/clang -target x86_64-apple-darwin11 -B /builds/worker/workspace/build/src/cctools/bin -isysroot /builds/worker/workspace/build/src/MacOSX10.11.sdk -std=gnu99 -Wl,--version` [task 2018-07-20T21:49:53.782Z] 21:49:53 INFO - ERROR: Failed to find a linker [task 2018-07-20T21:49:53.809Z] 21:49:53 INFO - *** Fix above errors and then restart with\ [task 2018-07-20T21:49:53.809Z] 21:49:53 INFO - "/usr/bin/make -f client.mk build" [task 2018-07-20T21:49:53.809Z] 21:49:53 INFO - client.mk:123: recipe for target 'configure' failed [task 2018-07-20T21:49:53.809Z] 21:49:53 INFO - make: *** [configure] Error 1 [task 2018-07-20T21:49:53.884Z] 21:49:53 ERROR - Return code: 2 [task 2018-07-20T21:49:53.884Z] 21:49:53 WARNING - setting return code to 2 [task 2018-07-20T21:49:53.884Z] 21:49:53 FATAL - 'mach build -v' did not run successfully. Please check log for errors. [task 2018-07-20T21:49:53.884Z] 21:49:53 FATAL - Running post_fatal callback... [task 2018-07-20T21:49:53.884Z] 21:49:53 FATAL - Exiting -1 [task 2018-07-20T21:49:53.885Z] 21:49:53 INFO - [mozharness: 2018-07-20 21:49:53.885096Z] Finished build step (failed) [task 2018-07-20T21:49:53.885Z] 21:49:53 INFO - Running post-run listener: _summarize [task 2018-07-20T21:49:53.885Z] 21:49:53 ERROR - # TBPL FAILURE # [task 2018-07-20T21:49:53.885Z] 21:49:53 INFO - [mozharness: 2018-07-20 21:49:53.885458Z] FxDesktopBuild summary: [task 2018-07-20T21:49:53.885Z] 21:49:53 ERROR - # TBPL FAILURE # [task 2018-07-20T21:49:53.885Z] 21:49:53 INFO - Running post-run listener: copy_logs_to_upload_dir [task 2018-07-20T21:49:53.885Z] 21:49:53 INFO - Copying logs to upload dir...

This looks to have appeared in this timeframe: https://treeherder.mozilla.org/#/jobs?repo=try&tochange=a2eccaed55592ae73a5a496501c619449ec592ba&fromchange=763b5cdf02e7da07a3b30b29611f38d660427dbc&filter-searchStr=cross

I assume this was bug 1451104 ?

Backed out bug 1451104 https://hg.mozilla.org/integration/mozilla-inbound/rev/dcfd01a3010b233490bafa693e51cd96f3ab5ce4 but those builds failed on the backout push https://treeherder.mozilla.org/#/jobs?repo=mozilla-inbound&revision=dcfd01a3010b233490bafa693e51cd96f3ab5ce4&filter-resultStatus=testfailed&filter-resultStatus=busted&filter-resultStatus=exception&filter-searchStr=OS%20X%20Cross%20Compiled&selectedJob=189282523 That didn't seem to have triggered new mac builds. So I've let one autoland push through to see if that would trigger new builds and see if the issue got solved: https://treeherder.mozilla.org/#/jobs?repo=autoland&filter-resultStatus=testfailed&filter-resultStatus=busted&filter-resultStatus=exception&filter-resultStatus=success&filter-resultStatus=pending&filter-resultStatus=running&filter-classifiedState=unclassified&filter-searchStr=OS%20X%20Cross&tochange=3bbf774e9e48ddd2cd34692f3ae18016af32c640&fromchange=18f56efc409395f86ff7cbc5a59c645ec2360099 Glandium helped along the way and he explained more about the clang workflow. This seemed to eventually solved the issue so reopening the trees.