There's no need to include this specific flag just for android. We can
already deal with what it tries to solve by using -C linker=/path/to/cc
and -C ar=/path/to/ar. The Makefiles for rustc already set this up when
we're crosscompiling.
I did add the flag to compiletest though so it can find gdb. Though, I'm
pretty sure we don't run debuginfo tests on android anyways right now.
[breaking-change]
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