Add back cmake export file

Add the EXPORT component for the header install components.

Author: steve-downey

CMakeLists.txt

@@ -37,7 +37,7 @@ set(CMAKE_VERIFY_INTERFACE_HEADER_SETS ON)
 add_library(beman_optional26 INTERFACE)
 target_sources(
     beman_optional26
-    PUBLIC FILE_SET beman_optional26_headers TYPE HEADERS BASE_DIRS src include
+    PUBLIC FILE_SET beman_optional26_headers TYPE HEADERS BASE_DIRS include
 )
 
 if(OPTIONAL26_ENABLE_TESTING)

include/beman/optional26/CMakeLists.txt

@@ -20,3 +20,22 @@ install(
         DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
         COMPONENT beman_optional26_development
 )
+
+install(
+    TARGETS beman_optional26
+    EXPORT beman_optional26_export
+    DESTINATION
+    ${CMAKE_INSTALL_LIBDIR}
+    FILE_SET beman_optional26_headers
+        DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
+        COMPONENT beman_optional26_development
+)
+
+install(
+    EXPORT beman_optional26_export
+    DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/beman/optional26/
+    NAMESPACE Beman::Optional26::
+    FILE beman_optional26.cmake
+    EXPORT_LINK_INTERFACE_LIBRARIES
+    COMPONENT beman_optional26_development
+)