[testing] run FileCheck with complete path

Otherwise, unless you happen to have FileCheck in your PATH, when you
copy/paste a test invocation to reproduce it, it fails.

Author: Dave Abrahams

test/lit.cfg

@@ -285,6 +285,7 @@ config.llvm_link = inferSwiftBinary('llvm-link')
 config.swift_llvm_opt = inferSwiftBinary('swift-llvm-opt')
 config.llvm_profdata = inferSwiftBinary('llvm-profdata')
 config.llvm_cov = inferSwiftBinary('llvm-cov')
+config.filecheck = inferSwiftBinary('FileCheck')
 
 config.swift_utils = os.path.join(config.swift_src_root, 'utils')
 config.line_directive = os.path.join(config.swift_utils, 'line-directive')
@@ -1007,11 +1008,12 @@ config.substitutions.append(('%llvm-cov', config.llvm_cov))
 
 config.substitutions.append(
     ('%FileCheck',
-     '%s --sanitize \'BUILD_DIR=%s\' --sanitize \'SOURCE_DIR=%s\'' %
+     '%s --sanitize \'BUILD_DIR=%s\' --sanitize \'SOURCE_DIR=%s\' --use-filecheck \'%s\'' %
       (config.PathSanitizingFileCheck,
        pipes.quote(swift_obj_root),
-       pipes.quote(config.swift_src_root))))
-config.substitutions.append(('%raw-FileCheck', 'FileCheck'))
+       pipes.quote(config.swift_src_root),
+       pipes.quote(config.filecheck))))
+config.substitutions.append(('%raw-FileCheck', pipes.quote(config.filecheck)))
 
 # If static stdlib is present, enable static stdlib tests
 static_stdlib_path = os.path.join(os.path.join(config.swift_lib_dir,"swift_static"), config.target_sdk_name)

utils/PathSanitizingFileCheck

@@ -33,14 +33,22 @@ constants.""")
         dest="sanitize_strings",
         default=[])
 
+    parser.add_argument(
+        "--use-filecheck",
+        help="path to LLVM FileCheck executable",
+        metavar="PATH",
+        action="store",
+        dest="file_check_path",
+        default="FileCheck")
+
     args, unknown_args = parser.parse_known_args()
 
     stdin = sys.stdin.read()
     for s in args.sanitize_strings:
         replacement, pattern = s.split('=', 1)
         stdin = stdin.replace(pattern, replacement)
 
-    p = subprocess.Popen(["FileCheck"] + unknown_args, stdin=subprocess.PIPE)
+    p = subprocess.Popen([args.file_check_path] + unknown_args, stdin=subprocess.PIPE)
     stdout, stderr = p.communicate(stdin)
     if stdout is not None:
         print(stdout)