A bunch of CMake fixes (#497)

CMakeLists.txt

@@ -1,35 +1,21 @@
-cmake_minimum_required(VERSION 3.9)
+cmake_minimum_required(VERSION 3.9...3.31)
 project(aws-c-http C)
 
 option(ENABLE_PROXY_INTEGRATION_TESTS "Whether to run the proxy integration tests that rely on pre-configured proxy" OFF)
 option(ENABLE_LOCALHOST_INTEGRATION_TESTS "Whether to run the integration tests that rely on pre-configured localhost" OFF)
 
-if (DEFINED CMAKE_PREFIX_PATH)
-    file(TO_CMAKE_PATH "${CMAKE_PREFIX_PATH}" CMAKE_PREFIX_PATH)
+if (NOT IN_SOURCE_BUILD)
+    # this is required so we can use aws-c-common's CMake modules
+    find_package(aws-c-common REQUIRED)
 endif()
 
-if (DEFINED CMAKE_INSTALL_PREFIX)
-    file(TO_CMAKE_PATH "${CMAKE_INSTALL_PREFIX}" CMAKE_INSTALL_PREFIX)
-endif()
-
-if (UNIX AND NOT APPLE)
-    include(GNUInstallDirs)
-elseif(NOT DEFINED CMAKE_INSTALL_LIBDIR)
-    set(CMAKE_INSTALL_LIBDIR "lib")
-endif()
-
-# This is required in order to append /lib/cmake to each element in CMAKE_PREFIX_PATH
-set(AWS_MODULE_DIR "/${CMAKE_INSTALL_LIBDIR}/cmake")
-string(REPLACE ";" "${AWS_MODULE_DIR};" AWS_MODULE_PATH "${CMAKE_PREFIX_PATH}${AWS_MODULE_DIR}")
-# Append that generated list to the module search path
-list(APPEND CMAKE_MODULE_PATH ${AWS_MODULE_PATH})
-
 include(AwsCFlags)
 include(AwsCheckHeaders)
 include(AwsSharedLibSetup)
 include(AwsSanitizers)
 include(CheckCCompilerFlag)
 include(AwsFindPackage)
+include(GNUInstallDirs)
 
 file(GLOB AWS_HTTP_HEADERS
         "include/aws/http/*.h"
@@ -71,7 +57,7 @@ target_link_libraries(${PROJECT_NAME} PUBLIC ${DEP_AWS_LIBS})
 aws_prepare_shared_lib_exports(${PROJECT_NAME})
 
 aws_check_headers(${PROJECT_NAME} ${AWS_HTTP_HEADERS})
-install(FILES ${AWS_HTTP_HEADERS} DESTINATION "include/aws/http")
+install(FILES ${AWS_HTTP_HEADERS} DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/aws/http")
 
 if (BUILD_SHARED_LIBS)
    set (TARGET_DIR "shared")
@@ -80,7 +66,7 @@ else()
 endif()
 
 install(EXPORT "${PROJECT_NAME}-targets"
-        DESTINATION "${LIBRARY_DIRECTORY}/${PROJECT_NAME}/cmake/${TARGET_DIR}/"
+        DESTINATION "${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME}/${TARGET_DIR}/"
         NAMESPACE AWS::
         COMPONENT Development)
 
@@ -89,7 +75,7 @@ configure_file("cmake/${PROJECT_NAME}-config.cmake"
         @ONLY)
 
 install(FILES "${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}-config.cmake"
-        DESTINATION "${LIBRARY_DIRECTORY}/${PROJECT_NAME}/cmake/"
+        DESTINATION "${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME}/"
         COMPONENT Development)
 
 include(CTest)

bin/elasticurl/CMakeLists.txt

@@ -1,7 +1,5 @@
 project(elasticurl C)
 
-list(APPEND CMAKE_MODULE_PATH "${CMAKE_INSTALL_PREFIX}/lib/cmake")
-
 file(GLOB ELASTICURL_SRC
         "*.c"
         )
@@ -25,5 +23,5 @@ install(TARGETS ${ELASTICURL_PROJECT_NAME}
         EXPORT ${ELASTICURL_PROJECT_NAME}-targets
         COMPONENT Runtime
         RUNTIME
-        DESTINATION bin
+        DESTINATION ${CMAKE_INSTALL_BINDIR}
         COMPONENT Runtime)