Fix test suite lookup path for LLDB.h

[beanz]

Summary

When running on Darwin, the test suite assumes a specific directory structure for the build directory. This works for the Xcode project builds, but fails for CMake builds regardless of whether or not you are generating the LLDB framework.

This patch allows the Darwin code path to fall back to the more generic code path used by other platforms in the event that LLDB.h isn't where the test suite expects it.

This allows API tests to run on Darwin when building with CMake with the framework build enabled or disabled.

[labath]

Our darwin buildbot is also running the local test suite with cmake: http://lab.llvm.org:8011/builders/lldb-x86_64-darwin-13.4, look under build step "test9 local test". We've been considering turning these tests off as we don't have bandwidth to monitor and fix them, but if you find them helpful, we can certainly keep them running.

[beanz]

@labath I think having them running is useful. At the moment that is probably the only Darwin bot building LLDB using CMake.

[tfiala]

(Retro) LGTM.

lldb/trunk/packages/Python/lldbsuite/test/decorators.py

def are_sb_headers_missing():
         if lldbplatformutil.getHostPlatform() == 'darwin':
             header = os.path.join(
                 os.environ["LLDB_LIB_DIR"],
                 'LLDB.framework',
                 'Versions',
                 'Current',
                 'Headers',
                 'LLDB.h')
-        else:
-            header = os.path.join(
-                os.environ["LLDB_SRC"],
-                "include",
-                "lldb",
-                "API",
-                "LLDB.h")
+            if os.path.exists(header):
+                return None
+        
         if not os.path.exists(header):
             return "skip because LLDB.h header not found"
         return None
 
     return skipTestIfFn(are_sb_headers_missing)(func)
 
 
 def skipIfiOSSimulator(func):