Avoid duplicating destdir in gcc/config.gcc after a second run
Avoid duplicating destdir in gcc/config.gcc after a second run

Test if the changes to gcc/config.gcc have already been applied before
making more changes.
If gcc's stage_2 fails and the user decides to re-run it and if $destdir
has "/opt", gcc/config.gcc would end up with with an invalid path.

Signed-off-by: Tulio Magno Quites Machado Filho <0e1b3d0765ee75ed64fa2e34822e4949a70a1429@linux.ibm.com>

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