CMake versions newer than ~3.1x automatically determine the subdirectory under CMAKE_INSTALL_PREFIX using the type of the installed target. Older versions need this to be manually computed using the GNUInstallDirs library.
Since we override the CMAKE_INSTALL_PREFIX default, this just controls
the internal layout of the install/ directory generated underneath the
boringssl checkout.
Bug: 488
Change-Id: I97b02006301e463bb0cfd54acb2b27656484cc85
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/52345
Reviewed-by: Adam Langley <agl@google.com>
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>