[TF] Change macOS tensorflow preset from release debug info to release.

[dan-zheng]

Workaround for TF-597: IRGenDebugInfo crash.

[dan-zheng]

Verified that this fixes building macOS toolchains:

-- Codesign xctoolchain --
+ /Users/danielzheng/swift-toolchain/swift/utils/toolchain-codesign lldb_codesign /Users/danielzheng/swift-toolchain/swift/swift-nightly-install//Library/Developer/Toolchains/swift-tensorflow-LOCAL-2019-06-23-a.xctoolchain/
-- Create Installer --
+ /Users/danielzheng/swift-toolchain/swift/utils/toolchain-installer /Users/danielzheng/swift-toolchain/swift/swift-nightly-install//Library/Developer/Toolchains/swift-tensorflow-LOCAL-2019-06-23-a.xctoolchain/ com.google.swift.20190623 '' swift-tensorflow-LOCAL-2019-06-23-a-osx.pkg /Library/Developer/Toolchains/swift-tensorflow-LOCAL-2019-06-23-a.xctoolchain swift-tensorflow-LOCAL-2019-06-23-a /Users/danielzheng/swift-toolchain/swift/utils/darwin-installer-scripts
pkgbuild: Inferring bundle components from contents of /Users/danielzheng/swift-toolchain/swift/swift-nightly-install//Library/Developer/Toolchains/swift-tensorflow-LOCAL-2019-06-23-a.xctoolchain/
pkgbuild: Adding component at usr/lib/sourcekitd.framework/Versions/A/XPCServices/SourceKitService.xpc
pkgbuild: Adding component at System/Library/PrivateFrameworks/LLDB.framework
pkgbuild: Adding component at usr/lib/sourcekitd.framework
pkgbuild: Adding top-level postinstall script
pkgbuild: Wrote package to swift-tensorflow-LOCAL-2019-06-23-a-osx.pkg

[dan-zheng]

@swift-ci Please test tensorflow

[burmako]

LGTM