[build_script] Use built XCTest for Linux tests

Previously, tests on Linux could only be run using the installed
swift-corelibs-xctest. Modify the script to use the built XCTest
instead of the installed one.

In addition, since the script no longer relies on the installed
XCTest, move the `--test` logic such that it can be used even
if `--module-install-path` and `--library-install-path` are not
specified.

Author: modocache

Tests/Functional/lit.cfg

@@ -28,14 +28,20 @@ def _getenv(name):
             'run.'.format(name))
     return value
 
-swift_exec = [_getenv('SWIFT_EXEC')]
+built_products_dir = _getenv('BUILT_PRODUCTS_DIR')
+swift_exec = [
+    _getenv('SWIFT_EXEC'),
+    '-Xlinker', '-rpath',
+    '-Xlinker', built_products_dir,
+    '-L', built_products_dir,
+    '-I', built_products_dir,
+]
 
 if platform.system() == 'Darwin':
     # On OS X, we need to make sure swiftc references the
     # proper SDK, has a deployment target set, and more...
     # Here we rely on environment variables, produced by xcodebuild.
     sdk_root = _getenv('SDKROOT')
-    built_products_dir = _getenv('BUILT_PRODUCTS_DIR')
     platform_name = _getenv('PLATFORM_NAME')
     deployment_target = _getenv('MACOSX_DEPLOYMENT_TARGET')
 
@@ -44,11 +50,8 @@ if platform.system() == 'Darwin':
     swift_exec.extend([
         '-sdk', sdk_root,
         '-target', target,
-        '-L', built_products_dir,
-        '-I', built_products_dir,
         '-F', built_products_dir,
-        '-Xlinker', '-rpath',
-        '-Xlinker', built_products_dir])
+    ])
 
 # Having prepared the swiftc command, we set the substitution.
 config.substitutions.append(('%{swiftc}', ' '.join(swift_exec)))

build_script.py

@@ -136,16 +136,19 @@ def main():
         cmd = ['cp', os.path.join(build_dir, install_mod_doc), os.path.join(module_path, install_mod_doc)]
         subprocess.check_call(cmd)
 
-        if args.test:
-            lit_path = os.path.join(
-                os.path.dirname(SOURCE_DIR), 'llvm', 'utils', 'lit', 'lit.py')
-            lit_flags = '-sv --no-progress-bar'
-            tests_path = os.path.join(SOURCE_DIR, 'Tests', 'Functional')
-            run('SWIFT_EXEC={swiftc} {lit_path} {lit_flags} '
-                '{tests_path}'.format(swiftc=swiftc,
-                                      lit_path=lit_path,
-                                      lit_flags=lit_flags,
-                                      tests_path=tests_path))
+    if args.test:
+        lit_path = os.path.join(
+            os.path.dirname(SOURCE_DIR), 'llvm', 'utils', 'lit', 'lit.py')
+        lit_flags = '-sv --no-progress-bar'
+        tests_path = os.path.join(SOURCE_DIR, 'Tests', 'Functional')
+        run('SWIFT_EXEC={swiftc} '
+            'BUILT_PRODUCTS_DIR={built_products_dir} '
+            '{lit_path} {lit_flags} '
+            '{tests_path}'.format(swiftc=swiftc,
+                                  built_products_dir=build_dir,
+                                  lit_path=lit_path,
+                                  lit_flags=lit_flags,
+                                  tests_path=tests_path))
 
     note('Done.')