Fix typo

Author: kitasuke

build-script.py

@@ -472,12 +472,12 @@ def main():
     testing_group.add_argument('--swift-build-exec', default='swift build',
                                help='''
       Path to the swift-build executable that is used to build SwiftPM projects
-      If not specified the the 'swift build' command will be used.
+      If not specified the 'swift build' command will be used.
       ''')
     testing_group.add_argument('--swift-test-exec', default='swift test',
                                help='''
       Path to the swift-test executable that is used to test SwiftPM projects
-      If not specified the the 'swift test' command will be used.
+      If not specified the 'swift test' command will be used.
       ''')
     testing_group.add_argument('--swiftc-exec', default='swiftc', help='''
       Path to the swift executable. If not specified the swiftc exeuctable