[Mips] Call findMIPSABIDirSuffix() for MIPS targets only.
[Mips] Do not detect a used MIPS toolchain. Build a path suffix for FSF
toolchain first and check the path existence. If the path does not
exist build and check a path suffix for Code Sourcery toolchain.
[Mips] Merge two MIPS Code Sourcery toolchain tests into the single one.
[Mips] Add support for nan2008 libraries and headers look up for Code
Sourcery MIPS toolchain.
[Mips] Reduce number of FileCheck variables used in the tests.
[Mips] Replace explicit argument handling by the single ArgList::AddLastArg() call.