[lldb] [lldbtest] Fix getBuildFlags() not to use libstdc++ on NetBSD

[mgorny]

Summary

Remove the code forcing -stdlib=libstdc++ on NetBSD in getBuildFlags()
method. NetBSD uses libc++ everywhere else, and using libstdc++ here
causes lang/cpp/dynamic-value to fail to build.

NB: I have no clue what getBuildFlags() is supposed to do, and why it's used in the few tests it's used in, so the change can be entirely wrong. However, tests pass for me with it, and it fixes missing symbols I've had when building with libstdc++.

[labath]

hmm.. interesting. I had no idea this function even exists. It's existence if unfortunate as it seems to duplicate some of the logic already present in makefiles, but that's not your problem here.

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

def getBuildFlags(
                 cflags += "c++0x"
             else:
                 cflags += "c++11"
         if self.platformIsDarwin() or self.getPlatform() == "freebsd":
             cflags += " -stdlib=libc++"
         elif self.getPlatform() == "openbsd":
             cflags += " -stdlib=libc++"
         elif self.getPlatform() == "netbsd":
-            cflags += " -stdlib=libstdc++"
+            # NetBSD defaults to libc++
+            pass
         elif "clang" in self.getCompiler():
             cflags += " -stdlib=libstdc++"
 
         return {'CFLAGS_EXTRAS': cflags,
                 'LD_EXTRAS': ldflags,
                 }
 
     def cleanup(self, dictionary=None):