Skip T13767 on Darwin

The CI job fails with:

	+++ rts/T13676.run/T13676.run.stderr.normalised	2019-10-09 12:27:56.000000000 -0700
	@@ -0,0 +1,4 @@
	+dyld: Library not loaded: @rpath/libHShaskeline-0.7.5.0-ghc8.9.0.20191009.dylib
	+  Referenced from: /Users/builder/builds/ewzE5N2p/0/ghc/ghc/inplace/lib/bin/ghc
	+  Reason: image not found
	+*** Exception: readCreateProcess: '/Users/builder/builds/ewzE5N2p/0/ghc/ghc/inplace/lib/bin/ghc' '-B/Users/builder/builds/ewzE5N2p/0/ghc/ghc/inplace/lib' '-e' ''/''$'/'' == '/''/x0024'/''' +RTS '-tT13676.t'  (exit -6): failed

Unable to reproduce locally.
21 jobs for master in 252 minutes and 59 seconds (queued for 4 seconds)
Status Job ID Name Coverage
  Lint
passed #176550
lint
lint-linters

00:00:14

passed #176553
lint
lint-submods-branch

00:00:16

passed #176551
lint
lint-testsuite

00:00:16

passed #176552
lint
typecheck-testsuite

00:00:13

 
  Build
passed #176555
x86_64-linux
hadrian-ghc-in-ghci

00:13:12

passed #176557
x86_64-linux
release-x86_64-linux-deb9-dwarf

00:55:26

passed #176556
x86_64-linux
validate-x86_64-linux-deb9-debug

01:21:38

passed #176554
x86_64-linux
validate-x86_64-linux-deb9-hadrian

01:20:57

 
  Full Build
failed #176559
aarch64-linux allowed to fail
validate-aarch64-linux-deb9

01:00:27

passed #176560
x86_64-linux
validate-i386-linux-deb9

00:39:21

passed #176558
x86_64-darwin
validate-x86_64-darwin

00:55:06

passed #176561
x86_64-linux
validate-x86_64-linux-deb9-integer-simple

01:44:56

passed #176562
x86_64-linux
validate-x86_64-linux-deb9-unreg

01:16:27

failed #176563
x86_64-linux
validate-x86_64-linux-fedora27

01:47:36

failed #176565
x86_64-windows allowed to fail
validate-x86_64-windows

00:42:42

failed #176564
x86_64-windows allowed to fail
validate-x86_64-windows-hadrian

02:50:41

 
  Cleanup
passed #176566
x86_64-darwin
cleanup-darwin

00:00:05

 
  Packaging
skipped #176567
x86_64-linux allowed to fail
doc-tarball
 
  Testing
skipped #176568
x86_64-linux allowed to fail manual
hackage
skipped #176569
x86_64-linux
perf-nofib
 
  Deploy
skipped #176570
x86_64-linux allowed to fail
pages
 
Name Stage Failure
failed
validate-aarch64-linux-deb9 Full Build
$ cp -Rf $HOME/.cabal cabal-cache
Uploading artifacts...
WARNING: ghc-*.tar.xz: no matching files
WARNING: junit.xml: no matching files
ERROR: No files to upload
Uploading artifacts...
WARNING: junit.xml: no matching files
ERROR: No files to upload
ERROR: Job failed: exit code 1
failed
validate-x86_64-linux-fedora27 Full Build
$ cp -Rf $HOME/.cabal cabal-cache
Uploading artifacts...
ghc-*.tar.xz: found 1 matching files
junit.xml: found 1 matching files

Uploading artifacts to coordinator... ok
id=176563 responseStatus=201 Created token=YpQzugDJ
Uploading artifacts...
junit.xml: found 1 matching files

Uploading artifacts to coordinator... ok
id=176563 responseStatus=201 Created token=YpQzugDJ
ERROR: Job failed: exit code 1
failed
validate-x86_64-windows-hadrian Full Build
junit.xml: found 1 matching files                  
WARNING: Failed to load system CertPool:crypto/x509: system root pool is not available on Windows
Uploading artifacts to coordinator... ok
id=176564 responseStatus=201 Created token=zixoHC2p
Uploading artifacts...
Runtime platform
arch=amd64 os=windows pid=1304 revision=1f513601 version=11.10.1
junit.xml: found 1 matching files

WARNING: Failed to load system CertPool:crypto/x509: system root pool is not available on Windows
Uploading artifacts to coordinator... ok
id=176564 responseStatus=201 Created token=zixoHC2p
ERROR: Job failed: exit status 1
failed
validate-x86_64-windows Full Build
Runtime platform                                    arch=amd64 os=windows pid=3116 revision=1f513601 version=11.10.1
WARNING: ghc-*.tar.xz: no matching files
WARNING: junit.xml: no matching files
ERROR: No files to upload
Uploading artifacts...
Runtime platform
arch=amd64 os=windows pid=4304 revision=1f513601 version=11.10.1
WARNING: junit.xml: no matching files
ERROR: No files to upload
ERROR: Job failed: exit status 2