patch 8.1.2358: tests fail on Cirrus CI for FreeBSD

Problem:    Tests fail on Cirrus CI for FreeBSD.
Solution:   Fix a test and skip some. (Christian Brabandt, closes #5281)
diff --git a/src/testdir/test_normal.vim b/src/testdir/test_normal.vim
index bbb9993..a28a825 100644
--- a/src/testdir/test_normal.vim
+++ b/src/testdir/test_normal.vim
@@ -1204,7 +1204,8 @@
     return
   endif
 
-  if has('mac') || has('bsd')
+  let not_gnu_man = has('mac') || has('bsd')
+  if not_gnu_man
     " In MacOS and BSD, the option for specifying a pager is different
     set keywordprg=man\ -P\ cat
   else
@@ -1213,7 +1214,7 @@
   " Test for using man
   2
   let a = execute('unsilent norm! K')
-  if has('mac')
+  if not_gnu_man
     call assert_match("man -P cat 'man'", a)
   else
     call assert_match("man --pager=cat 'man'", a)