link-arch doesn't appear to work on arm with gcc

[SeanTAllen]

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This might be more extensive than gcc. I assume it impacts clang as well.

The link-arch that we set is done using the -march option to the c compiler on link. -march is ignored on arm from my testing. Or rather, I can set it to junk like "foo" and it still compiles fine, whereas on x86, that results in a failure at link time.

gcc version:

gcc (Ubuntu 9.3.0-17ubuntu1~20.04) 9.3.0