Store absolute path for lldb executable in dotest.py

Summary:
lldb-server tests are currently being skipped on the
check-lldb target. This is because we get the path of
lldb-server by modifying the path to the lldb executable.
However, by this point, we've changed directories, and a
relative path to the build/bin directory will no longer point
to the location of lldb-server.

Storing an absolute path solves this issue.

Reviewers: vharron, zturner, tfiala, labath

Subscribers: labath, lldb-commits, sas

Differential Revision: http://reviews.llvm.org/D19082

This is a cherry-pick of r267463

llvm-svn: 270131

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

@@ -309,7 +309,7 @@ def parseOptionsAndInitTestdirs():
         configuration.lldbFrameworkPath = args.framework
 
     if args.executable:
-        lldbtest_config.lldbExec = args.executable
+        lldbtest_config.lldbExec = os.path.realpath(args.executable)
 
     if args.p:
         if args.p.startswith('-'):