Refactored lldb executable name discovery

The lldb executable was referenced through the code by 7 different
(effectively) global variables.

global lldbExecutablePath
global lldbExecutable
os.environ['LLDB_EXEC']
os.environ['LLDB_TEST']
dotest.lldbExec
dotest.lldbHere
lldbtest.lldbExec

This change uses one global variable lldbtest_config.lldbExec to
replace them all.

Differential Revision: http://reviews.llvm.org/D9817

llvm-svn: 237600
diff --git a/lldb/test/lldbpexpect.py b/lldb/test/lldbpexpect.py
index ad7e51b..6563744 100644
--- a/lldb/test/lldbpexpect.py
+++ b/lldb/test/lldbpexpect.py
@@ -19,7 +19,7 @@
     def launch(self, timeout=None):
         if timeout is None: timeout = 30
         logfile = sys.stdout if self.TraceOn() else None
-        self.child = pexpect.spawn('%s %s' % (self.lldbHere, self.launchArgs()), logfile=logfile)
+        self.child = pexpect.spawn('%s %s' % (lldbtest_config.lldbExec, self.launchArgs()), logfile=logfile)
         self.child.timeout = timeout
         self.timeout = timeout