[LyX/master] Cmake build: Try to not use absolute paths for INSTALL

[Kornel Benko]

commit 53c5129d20ea1ce2904ab3e471f0748919f9c2ac
Author: Kornel Benko <kornel at lyx.org>
Date:   Tue May 5 08:10:33 2026 +0200

    Cmake build: Try to not use absolute paths for INSTALL
    
    Use of absolute path to install files is deprecated in latest cmake.
---
 CMakeLists.txt | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index d07a46f169..a18fd7f573 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -541,11 +541,11 @@ if(CMAKE_INSTALL_PREFIX_INITIALIZED_TO_DEFAULT)
  endif()
 
 if(UNIX)
-  set(SYSTEM_DATADIR "${CMAKE_INSTALL_PREFIX}/share")
+  set(SYSTEM_DATADIR "./share")
 elseif(CMAKE_INSTALL_PREFIX MATCHES "/lyx${LYX_INSTALL_SUFFIX}$")
   string(REGEX REPLACE "/lyx${LYX_INSTALL_SUFFIX}$" "/share" SYSTEM_DATADIR ${CMAKE_INSTALL_PREFIX})
 else()
-  set(SYSTEM_DATADIR "${CMAKE_INSTALL_PREFIX}")
+  set(SYSTEM_DATADIR ".")
 endif()
 
 if(NOT CMAKE_COMPILER_IS_GNUCXX)
@@ -599,9 +599,9 @@ else()
 	if(WIN32)
 		set(LYX_MAN_DIR_tmp "${CMAKE_BINARY_DIR}/usr/local/man/")
 	elseif(UNIX)
-		set(LYX_MAN_DIR_tmp "${CMAKE_INSTALL_PREFIX}/share/man/")
+		set(LYX_MAN_DIR_tmp "./share/man/")
 	else()
-		set(LYX_MAN_DIR_tmp "${CMAKE_INSTALL_PREFIX}/man/")
+		set(LYX_MAN_DIR_tmp "./man/")
 	endif()
 endif()
 if (NOT LYX_MAN_DIR_tmp EQUAL "${LYX_MAN_DIR}")