Implement the correct search for configuration files. llvmc will now try the following in this order:  1. -config-dir=/path/to/configs  2. LLVM_CONFIG_DIR=/path/to/configs  3. ~/.llvm/etc  4. $prefix/etc  5. /etc/llvm
Implement the correct search for configuration files. llvmc will now try
the following in this order:
 1. -config-dir=/path/to/configs
 2. LLVM_CONFIG_DIR=/path/to/configs
 3. ~/.llvm/etc
 4. $prefix/etc
 5. /etc/llvm


git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@15950 91177308-0d34-0410-b5e6-96231b3b80d8

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