Correctly define "zlib" feature.

We have "REQUIRES: zlib" in our test, but zlib was not defined,
so the test did not run on any platform.

llvm-svn: 274730

lld/test/lit.cfg

@@ -191,6 +191,10 @@ if lit_config.useValgrind:
 if execute_external:
     config.available_features.add('shell')
 
+# zlib compression library
+if config.have_zlib == "1":
+    config.available_features.add("zlib")
+
 # Running on Darwin OS
 if platform.system() in ['Darwin']:
     config.available_features.add('system-linker-mach-o')

lld/test/lit.site.cfg.in

@@ -8,6 +8,7 @@ config.lit_tools_dir = "@LLVM_LIT_TOOLS_DIR@"
 config.lld_obj_root = "@LLD_BINARY_DIR@"
 config.target_triple = "@TARGET_TRIPLE@"
 config.python_executable = "@PYTHON_EXECUTABLE@"
+config.have_zlib = "@HAVE_LIBZ@"
 
 # Support substitution of the tools and libs dirs with user parameters. This is
 # used when we can't determine the tool dir at configuration time.