[test] Fix another realpath->abspath.

This is a followup to 817b3a6fe3a4452eb61a2503c8beaa7267ca0351: in `builder_base` we should use abspath, not realpath, because the name is significant.
This is used by test cases that use `@skipIf(compiler="clang", compiler_version=['<', <version>])`

Author: rupprecht

lldb/packages/Python/lldbsuite/test/plugins/builder_base.py

@@ -34,7 +34,7 @@ def getCompiler():
     """Returns the compiler in effect the test suite is running with."""
     compiler = configuration.compiler if configuration.compiler else "clang"
     compiler = lldbutil.which(compiler)
-    return os.path.realpath(compiler)
+    return os.path.abspath(compiler)
 
 
 def getArchFlag():