cmake: use CMAKE_INSTALL_*DIR variables as are, if absolute

These variables can be set to absolute paths, in that case ${prefix}
shouldn't be prepended. CMAKE_INSTALL_FULL_*DIR variables could have
also been used, but that would hard-code the relativity to the prefix
pkg-config variable. See also:

https://cmake.org/cmake/help/latest/module/GNUInstallDirs.html

1 files changed, 10 insertions, 2 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index bede146..7ab04ab 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -569,8 +569,16 @@ if(ENABLE_LIBRESSL_INSTALL)
                 # Create pkgconfig files.
                 set(prefix      ${CMAKE_INSTALL_PREFIX})
                 set(exec_prefix \${prefix})
-                set(libdir      \${exec_prefix}/${CMAKE_INSTALL_LIBDIR})
-                set(includedir  \${prefix}/${CMAKE_INSTALL_INCLUDEDIR})
+                if(IS_ABSOLUTE ${CMAKE_INSTALL_LIBDIR})
+                        set(libdir      ${CMAKE_INSTALL_LIBDIR})
+                else()
+                        set(libdir      \${exec_prefix}/${CMAKE_INSTALL_LIBDIR})
+                endif()
+                if(IS_ABSOLUTE ${CMAKE_INSTALL_INCLUDEDIR})
+                        set(includedir  ${CMAKE_INSTALL_INCLUDEDIR})
+                else()
+                        set(includedir  \${prefix}/${CMAKE_INSTALL_INCLUDEDIR})
+                endif()
                 if(PLATFORM_LIBS)
                         string(REGEX REPLACE ";" " -l" PLATFORM_LDADD ";${PLATFORM_LIBS}")
                 endif()