patch 9.0.1881: Test_crash fails on Mac

Problem:  Test_crash fails on Mac
Solution: Skip test on Mac

Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/test_crash.vim b/src/testdir/test_crash.vim
index b6ae4d2..b841ccb 100644
--- a/src/testdir/test_crash.vim
+++ b/src/testdir/test_crash.vim
@@ -7,6 +7,8 @@
 func Test_crash1()
   CheckNotBSD
   CheckExecutable dash
+  " Test 7 fails on Mac ... 
+  CheckNotMac
 
   " The following used to crash Vim
   let opts = #{cmd: 'sh'}