Fix building tests without system headers on Darwin

Summary: Default installations of OS X do not have system headers installed at /usr/include. This patch allows the LLDB test executables to properly compile when built on a system without headers at /usr/include by specifying a default value for the apple-sdk flag as "macosx".

Reviewers: tfiala, zturner

Subscribers: lldb-commits

Differential Revision: https://reviews.llvm.org/D25487

llvm-svn: 284042

lldb/packages/Python/lldbsuite/test/dotest_args.py

@@ -75,7 +75,7 @@ def create_parser():
     group.add_argument('-C', '--compiler', metavar='compiler', dest='compilers', action='append', help=textwrap.dedent(
         '''Specify the compiler(s) used to build the inferior executables. The compiler path can be an executable basename or a full path to a compiler executable. This option can be specified multiple times.'''))
     if sys.platform == 'darwin':
-        group.add_argument('--apple-sdk', metavar='apple_sdk', dest='apple_sdk', help=textwrap.dedent(
+        group.add_argument('--apple-sdk', metavar='apple_sdk', dest='apple_sdk', default="macosx", help=textwrap.dedent(
             '''Specify the name of the Apple SDK (macosx, macosx.internal, iphoneos, iphoneos.internal, or path to SDK) and use the appropriate tools from that SDK's toolchain.'''))
     # FIXME? This won't work for different extra flags according to each arch.
     group.add_argument(