Always use the absolute path to swift-reflection-test

This makes it easier to reproduce errors when copying/pasting
iOS simulator run lines without having to hunt the binary down
or altering the PATH.

Author: bitjammer

test/lit.cfg

@@ -861,7 +861,7 @@ config.substitutions.append(
      (subst_target_swift_ide_test_mock_sdk,
       subst_target_swift_ide_test_mock_sdk_after)))
 config.substitutions.append(('%target-swift-ide-test', config.target_swift_ide_test))
-config.substitutions.append(('%target-swift-reflection-test', 'swift-reflection-test{variant_suffix}'.format(variant_suffix=config.variant_suffix)))
+config.substitutions.append(('%target-swift-reflection-test', lit.util.which('swift-reflection-test{variant_suffix}'.format(variant_suffix=config.variant_suffix), config.environment['PATH'])))
 config.substitutions.append(('%target-swift-reflection-dump', '{} {} {}'.format(config.swift_reflection_dump, '-arch', run_cpu)))
 config.substitutions.append(('%target-swiftc_driver', config.target_swiftc_driver))
 config.substitutions.append(('%target-swift-remoteast-test-with-sdk',