Update cmake version to 3.16.5

[drexin]

3.15.1 contains a bug that causes libraries that use the CMake Swift module to be built with -Onone, even in release mode.

[drexin]

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[compnerd]

LGTM, assuming @shahmishal doesn't have any concerns.

[shahmishal]

This will require additional changes to CI before this can be merged, please hold off from merging it.

[shahmishal]

20:00:39 -- Could NOT find OpenSSL, try to set the path to OpenSSL root folder in the system variable OPENSSL_ROOT_DIR (missing: OPENSSL_CRYPTO_LIBRARY OPENSSL_INCLUDE_DIR) 
20:00:39 CMake Error at Utilities/cmcurl/CMakeLists.txt:454 (message):
20:00:39   Could not find OpenSSL.  Install an OpenSSL development package or
20:00:39   configure CMake with -DCMAKE_USE_OPENSSL=OFF to build without OpenSSL.

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[drexin]

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[drexin]

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[drexin]

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[drexin]

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[drexin]

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[drexin]

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[drexin]

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[drexin]

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[drexin]

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[drexin]

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[drexin]

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[RLovelett]

Two questions:

1. Should the README also be updated?
2. Should the CMakeLists.txt be updated?

[compnerd]

@RLovelett - updating the README is probably a good idea. The CMakeLists.txt update - in its current state any version is less than useful as it is an implementation of CMake in CMake. The work to clean up the build system is still incomplete, but help is welcome!

[drexin]

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[drexin]

@compnerd @shahmishal Bumped version in README and CMakeLists.txt. I think it's better to at least fail when it doesn't have the correct version. WDYT? I also changed the version for swift-5.2-branch back to 3.15.1 in update-checkout-config.json, since we decided not to upgrade there.

[drexin]

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[shahmishal]

I don't think we should bump the CMakeLists.txt, README is fine. We don't want to force everyone to update to CMake 3.16.5 to build the Swift compiler.

[drexin]

Ok, makes sense. I'll revert that.

[drexin]

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[drexin]

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[drexin]

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[compnerd]

Sure, bumping both is fine, I just meant that it doesn’t really convey much at the moment.