patch 8.0.0285: tests fail with tiny build on Unix

Problem:    Tests fail with tiny build on Unix.
Solution:   Only set g:tester_HOME when build with the +eval feature.

src/testdir/unix.vim

@@ -2,9 +2,12 @@
 " Always use "sh", don't use the value of "$SHELL".
 set shell=sh
 
-" While some tests overwrite $HOME to prevent them from polluting user files,
-" we need to remember the original value so that we can tell external systems
-" where to ask about their own user settings.
-let g:tester_HOME = $HOME
+" Only when the +eval feature is present. 
+if 1
+  " While some tests overwrite $HOME to prevent them from polluting user files,
+  " we need to remember the original value so that we can tell external systems
+  " where to ask about their own user settings.
+  let g:tester_HOME = $HOME
+endif
 
 source setup.vim

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    285,
 /**/
     284,
 /**/