tree 90c7a864bad5f8cff22fbc2f4d11581863ffee28
parent 5b89336b4c89f7458d038141916815511f366437
author David Benjamin <davidben@google.com> 1560394099 -0400
committer Adam Langley <agl@google.com> 1560442262 +0000

Set a minimum CMake version of 3.0.

CMake 3.0 was released June 10, 2014, just over five years ago. Set the minimum
version to 3.0. This cleans up some Mac workarounds. (CMP0025 was introduced
in 3.0, so setting the minimum version to 3.0 also enables it.)

CMP0025 is important because Clang and Apple Clang use different version
numbers. Prior to CMake 3.0, both read as Clang. Starting CMake 3.0, with
CMP0025 enabled, they read as Clang and AppleClang. Without this, we cannot
sanely version-check clang.

Unfortunately, CMP0025 applies at compiler detection, so if BoringSSL is
imported as a CMake subproject, we are dependent on the root project setting
CMP0025. But if we successfully set a minumum of 3.0, we can reasonably ask
consumers to do the same, which will do so.

Next up: In December, we can raise the version to CMake 3.1, which adds support
for specifying C and C++ language versions in CMake. (Alternatively, Abseil's
minimum version is actually 3.5, so maybe we can update more aggressively
here.)

Update-Note: CMake 2.8 is no longer supported. Update your CMake to the latest
    version if it has not been updated in five years.

Change-Id: I3378567ad7575fc9fac69e05c403d69ea10332e2
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/36444
Reviewed-by: Adam Langley <agl@google.com>