'main': Use nice for tests in previous

stdbuf is not present on all systems. nice is not builtin and is POSIX.

highlighters/main/test-data/precommand-type1.zsh

@@ -30,7 +30,7 @@
 
 # Test the behaviour of a builtin that exists as a command as well.
 # The spaces in $BUFFER are to align precommand-type*.zsh test files.
-BUFFER=$'test  ; builtin test  ; builtin command test  ; stdbuf test  '
+BUFFER=$'test  ; builtin test  ; builtin command test  ; nice test  '
 
 # Our expectations assumes that a 'test' external command exists (in addition
 # to the 'test' builtin).  Let's verify that, using the EQUALS option (which
@@ -56,6 +56,6 @@ expected_region_highlight=(
   '41 44 command "issue #608"' # test
   '47 47 commandseparator' # ;
 
-  '49 54 precommand' # stdbuf
-  '56 59 command "issue #608"' # test
+  '49 52 precommand' # nice
+  '54 57 command "issue #608"' # test
 )

highlighters/main/test-data/precommand-type2.zsh

@@ -30,7 +30,7 @@
 
 # Test the behaviour of a builtin that does not exist as a command.
 # The spaces in $BUFFER are to align precommand-type*.zsh test files.
-BUFFER=$'zstyle; builtin zstyle; builtin command zstyle; stdbuf zstyle'
+BUFFER=$'zstyle; builtin zstyle; builtin command zstyle; nice zstyle'
 
 # Verify that no $^path/zstyle(N) binary exists.
 if (disable zstyle; type zstyle >/dev/null); then
@@ -50,6 +50,6 @@ expected_region_highlight=(
   '41 46 unknown-token "issue #608"' # zstyle
   '47 47 commandseparator' # ;
 
-  '49 54 precommand' # stdbuf
-  '56 61 unknown-token "issue #608"' # zstyle
+  '49 52 precommand' # nice
+  '54 59 unknown-token "issue #608"' # zstyle
 )

highlighters/main/test-data/precommand-type3.zsh

@@ -30,7 +30,7 @@
 
 # Test an external command that does not exist as a builtin.
 # The spaces in $BUFFER are to align precommand-type*.zsh test files.
-BUFFER=$'ls    ; builtin ls    ; builtin command ls    ; stdbuf ls    '
+BUFFER=$'ls    ; builtin ls    ; builtin command ls    ; nice ls    '
 
 # Verify that the 'ls' command isn't shadowed.
 if [[ $(type -w ls) != "ls: command" ]]; then
@@ -50,6 +50,6 @@ expected_region_highlight=(
   '41 42 command' # ls
   '47 47 commandseparator' # ;
 
-  '49 54 precommand' # stdbuf
-  '56 57 command' # ls
+  '49 52 precommand' # nice
+  '54 55 command' # ls
 )