Use __has_include rather than a configure-time macro to determine if <sys/resource.h> is available. This should fix out-of-tree builds, at the cost of not providing the higher rlimits to stage 1 clang when built with an old host compiler not implementing this feature yet (bootstrap builds should be fine, though).
Use __has_include rather than a configure-time macro to determine if
<sys/resource.h> is available. This should fix out-of-tree builds, at the cost
of not providing the higher rlimits to stage 1 clang when built with an old
host compiler not implementing this feature yet (bootstrap builds should be
fine, though).

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@279112 91177308-0d34-0410-b5e6-96231b3b80d8
(cherry picked from commit ca10d2e64d9630bb93507ac416c3f176d0df8a2b)

apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang