Fix builds when in a submodule

CMakeLists.txt

@@ -1,12 +1,20 @@
 cmake_minimum_required(VERSION 3.10)
 project(akstdlib LANGUAGES C)
 
+if(TARGET akerror::akerror)
+  message(STATUS "FOUND akerror::akerror")
+else()
+  message(STATUS "MISSING akerror::akerror")
+endif()
+
 include(CTest)
 include(GNUInstallDirs)
 include(CMakePackageConfigHelpers)
 
-find_package(PkgConfig REQUIRED)
-find_package(akerror REQUIRED)
+if(NOT TARGET akerror::akerror)
+  find_package(PkgConfig REQUIRED)
+  find_package(akerror REQUIRED)
+endif()
 
 set(akstdlib_install_cmakedir "${CMAKE_INSTALL_LIBDIR}/cmake/akstdlib")
 set(prefix      ${CMAKE_INSTALL_PREFIX})
@@ -19,6 +27,8 @@ add_library(akstdlib SHARED
   src/stdlib.c
 )
 
+add_library(akstdlib::akstdlib ALIAS akstdlib)
+
 # Specify include directories for the library's headers (if applicable)
 target_include_directories(akstdlib PUBLIC
   $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
@@ -28,7 +38,6 @@ target_include_directories(akstdlib PUBLIC
 target_link_libraries(akstdlib PUBLIC akerror::akerror)
 
 set(main_lib_dest "lib/my_library-${MY_LIBRARY_VERSION}")
-install(TARGETS akstdlib EXPORT akstdlib DESTINATION "lib/")
 install(TARGETS akstdlib
   EXPORT akstdlibTargets
   ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
@@ -37,13 +46,11 @@ install(TARGETS akstdlib
   INCLUDES DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
 )
 
-install(EXPORT akstdlib FILE akstdlibTargets.cmake DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/akstdlib)
-
 install(FILES "include/akstdlib.h" DESTINATION "include/")
 install(FILES ${CMAKE_CURRENT_BINARY_DIR}/akstdlib.pc DESTINATION "lib/pkgconfig/")
 
 
-install(EXPORT akstdlib
+install(EXPORT akstdlibTargets
     FILE akstdlibTargets.cmake
     NAMESPACE akstdlib::
     DESTINATION ${akstdlib_install_cmakedir}