[lldb] Mark UnsupportedLanguage.test Unsupported on Windows

This is to fix buildbot fallout post #156729 without needing to revert the
original patch.

Author: boomanaiden154

lldb/test/Shell/Process/UnsupportedLanguage.test

@@ -1,5 +1,10 @@
 Test unsupported language warning
 
+TODO: This test does not work on Windows, seemingly because the sed commands
+are not actually doing anything. This should be fixed so we can enable this on
+Windows.
+UNSUPPORTED: system-windows
+
 RUN: %clang_host %S/Inputs/true.c -std=c99 -g -c -S -emit-llvm -o - \
 RUN:   | sed -e 's/DW_LANG_C99/DW_LANG_Mips_Assembler/g' >%t.ll
 RUN: %clang_host %t.ll -g -o %t.exe