libtiff: Fix pkgconf file relative paths

https://github.com/libsdl-org/libtiff/commit/0fafae59799d9dc71a2969ca8cff632fc0929586

From 0fafae59799d9dc71a2969ca8cff632fc0929586 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Milo=C5=A1=20Komar=C4=8Devi=C4=87?=
 <miloskomarcevic@aim.com>
Date: Wed, 2 Mar 2022 19:00:00 +0000
Subject: [PATCH] Fix pkgconf file relative paths

---
 cmake/PkgConfig.cmake | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/cmake/PkgConfig.cmake b/cmake/PkgConfig.cmake
index 7796a6b7..4c193534 100644
--- a/cmake/PkgConfig.cmake
+++ b/cmake/PkgConfig.cmake
@@ -47,12 +47,12 @@ endfunction()
 
 # Generate pkg-config file
 set(prefix "${CMAKE_INSTALL_PREFIX}")
-set(exec_prefix "${CMAKE_INSTALL_PREFIX}")
-set(libdir "${CMAKE_INSTALL_LIBDIR}")
-set(includedir "${CMAKE_INSTALL_INCLUDEDIR}")
+set(exec_prefix "$${prefix}")
+set(libdir "$${exec_prefix}/${CMAKE_INSTALL_LIBDIR}")
+set(includedir "$${prefix}/${CMAKE_INSTALL_INCLUDEDIR}")
 set_libs_private(tiff_libs_private ${tiff_libs_private_list})
 configure_file(${CMAKE_CURRENT_SOURCE_DIR}/libtiff-4.pc.in
-        ${CMAKE_CURRENT_BINARY_DIR}/libtiff-4.pc)
+        ${CMAKE_CURRENT_BINARY_DIR}/libtiff-4.pc @ONLY)
 
 # Install pkg-config file
 install(FILES ${CMAKE_CURRENT_BINARY_DIR}/libtiff-4.pc