curl: Backport patch to fix buildtools issues

bitbake-selftest was failing on a github url on hosts using buildtools.
The issue was tracked down to the curl upgrade 8.6.0 -> 8.7.1. Whilst there
is a fix in upstream git to workaround the issue in this version, backport
the fix from curl upstream to ensure there are no other related issues to
the bug.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>