Simplify find_include_dirs

cmake/utils/find_include_dirs.cmake

@@ -1,30 +1,8 @@
 include_guard(GLOBAL)
 
-function(find_include_dirs OUT_VAR)
-    set(SOURCES ${ARGN})
-
-    # Get top most common directory prefix for all source files
-    set(COMMON_PATH "")
-    foreach(FILE IN LISTS SOURCES)
-        get_filename_component(DIR ${FILE} DIRECTORY)
-        file(REAL_PATH ${DIR} DIR)
-        if(COMMON_PATH STREQUAL "")
-            set(COMMON_PATH ${DIR})
-        else()
-            string(LENGTH ${COMMON_PATH} PREFIX_LEN)
-            while(NOT ${DIR} MATCHES "^${COMMON_PATH}(/|$)" AND PREFIX_LEN GREATER 0)
-                string(SUBSTRING ${COMMON_PATH} 0 ${PREFIX_LEN} COMMON_PATH)
-                math(EXPR PREFIX_LEN "${PREFIX_LEN} - 1")
-            endwhile()
-        endif()
-    endforeach()
-
-    if(NOT IS_DIRECTORY ${COMMON_PATH})
-        message(FATAL_ERROR "Could not determine common directory for source files")
-    endif()
-
-    # Recursively find directories that contain .h files under common directory
-    file(GLOB_RECURSE HEADER_FILES ${COMMON_PATH}/*.h)
+function(find_include_dirs OUT_VAR LIBRARY_DIR)
+    # Recursively find directories that contain .h files under LIBRARY_DIR
+    file(GLOB_RECURSE HEADER_FILES ${LIBRARY_DIR}/*.h)
     set(INCLUDE_DIRS "")
     foreach(HEADER_FILE IN LISTS HEADER_FILES)
         get_filename_component(HEADER_DIR ${HEADER_FILE} DIRECTORY)