Cmake incorrectly installs config files when passed absolute values

[jonringer]

protobuf/cmake/install.cmake

Lines 145 to 149 in 654c253

	install(DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/${CMAKE_INSTALL_CMAKEDIR}/
	DESTINATION "${CMAKE_INSTALL_CMAKEDIR}"
	COMPONENT protobuf-export
	PATTERN protobuf-targets.cmake EXCLUDE
	)

Is the offending offending section.

CMAKE_CURRENT_BINARY_DIR will be some build directory (e.g. /build/source/build/)
CMAKE_INSTALL_CMAKEDIR inherits from CMAKE_INSTALL_LIBDIR (e.g. /nix/store/x4bq4v508n8pxazh9137hcd64i40fvb0-protobuf-3.15.8/lib/cmake/protobuf)

The resultant /build/source/build//nix/store/x4bq4v508n8pxazh9137hcd64i40fvb0-protobuf-3.15.8/lib/cmake/protobuf is not a path which can install files.

What version of protobuf and what language are you using?
Version: 3.15, but still an issue in master
Language: C++

What operating system (Linux, Windows, ...) and version?

$ uname -a
Linux jon-desktop 5.4.188 #1-NixOS SMP Mon Mar 28 06:46:49 UTC 2022 x86_64 GNU/Linux

What runtime / compiler are you using (e.g., python version or gcc version)

$ gcc --version
gcc (GCC) 11.2.0
Copyright (C) 2021 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

What did you do?
Steps to reproduce the behavior:

cd cmake
mkdir build
cd build
cmake --build ..

What did you expect to see
It not fail to find directory

What did you see instead?
Failure around incorrect path

Make sure you include information that can help us debug (full error message, exception listing, stack trace, logs).

       > CMake Error at cmake_install.cmake:1693 (file):
       >   file INSTALL cannot find
       >   "/build/source/build//nix/store/x4bq4v508n8pxazh9137hcd64i40fvb0-protobuf-3.15.8/lib/cmake/protobuf":
       >   No such file or directory.

Anything else we should know about your project / environment
Using Nix