changed: move doxy target code to a macro

i forgot to test the common app build way of doing things.
this complicated things enough to warrant a macro

cmake/Modules/FindIFEM.cmake

@@ -156,3 +156,4 @@ if(NOT IFEM_TESTING_INCLUDED)
 endif()
 
 set(IFEM_REGTEST_SCRIPT ${IFEM_PATH}/Apps/Common/scripts/regtest.sh.in)
+include(../Scripts/IFEMDoxy)

cmake/Scripts/IFEMDoxy.cmake

@@ -0,0 +1,31 @@
+# Add the appropriate target to generate doxy for used build configuration
+macro(add_doc_target appname dox)
+  if(IFEM_AS_SUBMODULE OR IFEM_INTREE_BUILD)
+    configure_file(${IFEM_PATH}/doc/Doxyfile.in Doxyfile)
+  else()
+    configure_file(doc/Doxyfile.in Doxyfile)
+  endif()
+  configure_file(doc/${dox}.dox.in ${dox}.dox)
+
+  if(IFEM_INSTALL_DOXY)
+    install(CODE "EXECUTE_PROCESS(COMMAND ${CMAKE_BUILD_TOOL} doc WORKING_DIRECTORY \"${CMAKE_CURRENT_BINARY_DIR}\")" COMPONENT doc)
+    install(DIRECTORY ${PROJECT_BINARY_DIR}/doc/html DESTINATION ${CMAKE_INSTALL_DOCDIR}/Apps/${appname}
+            COMPONENT doc
+            PATTERN *.md5 EXCLUDE
+            PATTERN *.map EXCLUDE)
+  endif(IFEM_INSTALL_DOXY)
+
+  if(IFEM_COMMON_APP_BUILD)
+    if(NOT TARGET doc)
+      add_custom_target(doc)
+    endif()
+    add_custom_target(${appname}_doc doxygen ${PROJECT_BINARY_DIR}/Doxyfile
+                      WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}
+                      COMMENT "Generating API documentation" VERBATIM)
+    add_dependencies(doc ${appname}_doc)
+  else()
+    add_custom_target(doc doxygen ${PROJECT_BINARY_DIR}/Doxyfile
+                      WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}
+                      COMMENT "Generating API documentation" VERBATIM)
+  endif()
+endmacro()

cmake/Templates/IFEMConfig.cmake.in

@@ -21,4 +21,5 @@ if(NOT IFEM_FOUND)
   set_target_properties(IFEMAppCommon PROPERTIES IMPORTED_LOCATION
                         @CMAKE_INSTALL_PREFIX@/@CMAKE_INSTALL_LIBDIR@/libIFEMAppCommon${CMAKE_STATIC_LIBRARY_SUFFIX})
   set(IFEM_FOUND 1)
+  include(IFEMDoxy)
 endif()