Mark this test as unsupported on Windows systems

There is a strange issue happening with command line processing though. The
command line argument
   --export-dynamic-symbol 'f*'
does not have the single quotes stripped on some Windows targets (but not
all). This causes the glob matching to fail, which means the test fails on
some Windows bots and passes on others.

This is expected to be a temporary measure to get bots back to green. I've not
found a commit that has caused a behavioral change that could be reverted
instead, so this could be an issue with lit or test machine configuration.

Author: AaronBallman

lld/test/ELF/export-dynamic-symbol.s

@@ -1,5 +1,15 @@
 # REQUIRES: x86
 
+# FIXME: this should be supported on Windows as well. There is a strange issue
+# happening with command line processing though. The command line argument
+#   --export-dynamic-symbol 'f*'
+# does not have the single quotes stripped on some Windows targets (but not
+# all). This causes the glob matching to fail, which means the test fails on
+# some Windows bots and passes on others. However, there's no clear indication
+# as to what's changed to cause this behavior. Marking the test as unsupported
+# so that we have time to investigate the issue without losing postcommit CI.
+# UNSUPPORTED: system-windows
+
 # RUN: llvm-mc -filetype=obj -triple=x86_64 %s -o %t.o
 
 ## For an executable, --export-dynamic-symbol exports a symbol if it is non-local and defined.