[Support] Fix recursive response file expansion guard

Response file expansion limits the amount of expansion to prevent
potential infinite recursion. However, the current logic assumes that
any argument beginning with @ is a response file, which is not true for
e.g. `-Xlinker -rpath -Xlinker @executable_path/../lib` on Darwin.
Having too many of these non-response file arguments beginning with @
prevents actual response files from being expanded. Instead, limit based
on the number of successful response file expansions, which should still
prevent infinite recursion but also avoid false positives.

Differential Revision: https://reviews.llvm.org/D60631

llvm-svn: 358452