Support CMake 3.12.

Ubuntu 20.04 has 3.16, so requiring 3.17 is a bit mean.

.drone.yml

@@ -42,10 +42,10 @@ steps:
   - name: debian-package-cache
     path: /var/cache/apt/archives
 
-- name: Download CMake 3.17 installer
+- name: Download CMake 3.12 installer
   image: plugins/download
   settings:
-    source: https://cmake.org/files/v3.17/cmake-3.17.0-Linux-x86_64.sh
+    source: https://cmake.org/files/v3.12/cmake-3.12.0-Linux-x86_64.sh
     destination: cmake_installer.sh
 
 - name: GCC 7 / clang 6

CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.17...3.18)
+cmake_minimum_required(VERSION 3.12...3.18)
 
 # Global build options.
 set(CMAKE_BUILD_TYPE "Release" CACHE STRING "The type of build.")

README.adoc

@@ -43,7 +43,7 @@ image::https://repology.org/badge/vertical-allrepos/epubgrep.svg[]
 * Tested OS: Linux
 * C\++ compiler with C++17 support (tested: link:{uri-gcc}[GCC] 7/10,
   link:{uri-clang}[clang] 6/11)
-* link:{uri-cmake}[CMake] (at least: 3.17)
+* link:{uri-cmake}[CMake] (at least: 3.12)
 * link:{uri-boost}[Boost] (tested: 1.75.0 / 1.65.0)
 * link:{uri-gettext}[gettext] (tested: 0.21 / 0.19)
 * link:{uri-libarchive}[libarchive] (tested: 3.5 / 3.2)

src/CMakeLists.txt

@@ -21,9 +21,18 @@ target_link_libraries(${PROJECT_NAME}_lib
   Boost::program_options
   Boost::regex
   std::filesystem
-  LibArchive::LibArchive
   fmt::fmt)
 
+if(${CMAKE_VERSION} VERSION_LESS 3.17)
+  target_link_libraries(${PROJECT_NAME}_lib
+    PUBLIC ${LibArchive_LIBRARIES})
+  target_include_directories(${PROJECT_NAME}_lib
+    PUBLIC ${LibArchive_INCLUDE_DIRS})
+else()
+  target_link_libraries(${PROJECT_NAME}_lib
+    PUBLIC LibArchive::LibArchive)
+endif()
+
 target_include_directories(${PROJECT_NAME}_lib
   PUBLIC
   "$<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>"