From aa06a4761e24e59ceaa00e81be450b4d9a0c4d26 Mon Sep 17 00:00:00 2001
From: Eli Schwartz <eschwartz@archlinux.org>
Date: Mon, 27 Jul 2020 18:15:18 -0400
Subject: [PATCH] cmake: install pkg-config file relative to current_binary_dir

When the testsuite is enabled, the "cmake_add_subdirectory" test
adds a second copy of the project into the build configuration, and the
project files are installed twice.

This becomes super problematic when it tries to install a file from
CMAKE_BINARY_DIR which is only available in CMAKE_CURRENT_BINARY_DIR
and bombs out with the following error message:

```
[...]
-- Installing: <DESTDIR>/usr/lib/cmake/nlohmann_json/nlohmann_jsonTargets.cmake
CMake Error at test/cmake_add_subdirectory/nlohmann_json/cmake_install.cmake:73 (file):
  file INSTALL cannot find
  "......./nlohmann-json/builddir/test/cmake_add_subdirectory/nlohmann_json.pc":
  No such file or directory.
Call Stack (most recent call first):
  test/cmake_add_subdirectory/cmake_install.cmake:47 (include)
  test/cmake_install.cmake:49 (include)
  cmake_install.cmake:94 (include)
```
---
 CMakeLists.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index d5d0ae345f..1afcc25777 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -157,7 +157,7 @@ endif()
         DESTINATION ${NLOHMANN_JSON_CONFIG_INSTALL_DIR}
     )
     install(
-        FILES "${CMAKE_BINARY_DIR}/${PROJECT_NAME}.pc"
+        FILES "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}.pc"
         DESTINATION lib/pkgconfig
     )
 endif()