[cl-compat] Change /JMC from unsupported to ignored.
[cl-compat] Change /JMC from unsupported to ignored.

A tracking bug for actually implementing this in clang-cl is at
https://bugs.llvm.org/show_bug.cgi?id=39156.

Differential Revision: https://reviews.llvm.org/D52798

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@343629 91177308-0d34-0410-b5e6-96231b3b80d8

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