[lit] Mark ulimit test as unsupported on Solaris

160058f broke the Solaris bots because
they do not support RLIMIT_FSIZE despite it being in POSIX 2004. Disable
it there for now as the loss of test coverage should not be significant.

Author: boomanaiden154

llvm/utils/lit/tests/shtest-ulimit-nondarwin.py

@@ -2,7 +2,7 @@
 
 # ulimit does not work on non-POSIX platforms.
 # These tests are specific to options that Darwin does not support.
-# UNSUPPORTED: system-windows, system-darwin, system-aix
+# UNSUPPORTED: system-windows, system-darwin, system-aix, system-solaris
 
 # RUN: not %{lit} -a -v %{inputs}/shtest-ulimit-nondarwin | FileCheck %s