From 3286289bf699d37a85926ea62b0edd6901c85f40 Mon Sep 17 00:00:00 2001
From: Olivier Le Doeuff <olivier.ldff@gmail.com>
Date: Mon, 26 Sep 2022 16:38:54 +0200
Subject: [PATCH] build: use standard `CMAKE_INSTALL_INCLUDEDIR` for header
 install folder.

This gives user control over which folder header should be installed to instead of using hardcoded value `include/`.
Variable `CMAKE_INSTALL_INCLUDEDIR` is provided after a call to `include(GNUInstallDirs)`
More info can be found about usage in docs: https://cmake.org/cmake/help/latest/command/install.html
---
 CMakeLists.txt | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 12f0e46..d81ed81 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -68,10 +68,10 @@ add_library( date INTERFACE )
 add_library( date::date ALIAS date )
 target_include_directories( date INTERFACE
     $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
-    $<INSTALL_INTERFACE:include> )
+    $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}> )
 # adding header sources just helps IDEs
 target_sources( date INTERFACE
-    $<BUILD_INTERFACE:${CMAKE_CURRENT_LIST_DIR}/include>$<INSTALL_INTERFACE:include>/date/date.h
+    $<BUILD_INTERFACE:${CMAKE_CURRENT_LIST_DIR}/include>$<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>/date/date.h
     # the rest of these are not currently part of the public interface of the library:
     $<BUILD_INTERFACE:${CMAKE_CURRENT_LIST_DIR}/include/date/solar_hijri.h>
     $<BUILD_INTERFACE:${CMAKE_CURRENT_LIST_DIR}/include/date/islamic.h>
@@ -111,14 +111,14 @@ if( BUILD_TZ_LIB )
     add_library( date-tz )
     target_sources( date-tz
       PUBLIC
-        $<BUILD_INTERFACE:${CMAKE_CURRENT_LIST_DIR}/include>$<INSTALL_INTERFACE:include>/date/tz.h
+        $<BUILD_INTERFACE:${CMAKE_CURRENT_LIST_DIR}/include>$<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>/date/tz.h
       PRIVATE
         include/date/tz_private.h
         src/tz.cpp )
     if ( IOS )
       target_sources( date-tz
         PUBLIC
-          $<BUILD_INTERFACE:${CMAKE_CURRENT_LIST_DIR}/include>$<INSTALL_INTERFACE:include>/date/ios.h
+          $<BUILD_INTERFACE:${CMAKE_CURRENT_LIST_DIR}/include>$<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>/date/ios.h
         PRIVATE
           src/ios.mm )
     endif()
@@ -126,7 +126,7 @@ if( BUILD_TZ_LIB )
     target_link_libraries( date-tz PUBLIC date )
     target_include_directories( date-tz PUBLIC
         $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
-        $<INSTALL_INTERFACE:include> )
+        $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}> )
 
     if ( USE_SYSTEM_TZ_DB OR MANUAL_TZ_DB )
       target_compile_definitions( date-tz PRIVATE AUTO_DOWNLOAD=0 HAS_REMOTE_API=0 )