so it can't be completely fixed here. Putting -I paths to the current
headers in CFLAGS is more likely to break things than fix them, since
there is no reason why current headers should work with old libraries.
Other Makefiles that do this may only work because they are not used early
in the bootstrap. However, the usual problem with errno being defined in
terms of a nonexistent library doesn't seem to occur here, since we don't
reference errno.
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