cmake: headers: fix include warnings of disabled/system packages

cc1: warning: /home/thomas/external/fluent-bit/lib/<package>/include: No such file or directory [-Wmissing-include-dirs]

If luajit or nghttp2 are found on the system, then the include can be omitted.
If avro is disabled, then the include for jansson can be omitted.

Signed-off-by: Thomas Devoogdt <thomas@devoogdt.com>

cmake/headers.cmake

@@ -22,10 +22,6 @@ include_directories(
   ${FLB_PATH_ROOT_SOURCE}/${FLB_PATH_LIB_CHUNKIO}/include
   ${CMAKE_CURRENT_BINARY_DIR}/lib/chunkio/include
 
-  # LuaJIT
-  ${FLB_PATH_ROOT_SOURCE}/${FLB_PATH_LIB_LUAJIT}/src
-  ${CMAKE_CURRENT_BINARY_DIR}/lib/luajit-cmake
-
   ${FLB_PATH_ROOT_SOURCE}/${FLB_PATH_LIB_MONKEY}/include
   ${FLB_PATH_ROOT_SOURCE}/${FLB_PATH_LIB_MONKEY}/include/monkey
   ${FLB_PATH_ROOT_SOURCE}/${FLB_PATH_LIB_MBEDTLS}/include
@@ -36,21 +32,42 @@ include_directories(
   ${FLB_PATH_ROOT_SOURCE}/${FLB_PATH_LIB_SNAPPY}
   ${FLB_PATH_ROOT_SOURCE}/${FLB_PATH_LIB_CMETRICS}/include
   ${FLB_PATH_ROOT_SOURCE}/${FLB_PATH_LIB_CTRACES}/include
-  ${FLB_PATH_ROOT_SOURCE}/${FLB_PATH_LIB_CARES}/include
   ${FLB_PATH_ROOT_SOURCE}/${FLB_PATH_LIB_RING_BUFFER}/lwrb/src/include
 
-  ${CMAKE_CURRENT_BINARY_DIR}/${FLB_PATH_LIB_CARES}
-  ${CMAKE_CURRENT_BINARY_DIR}/${FLB_PATH_LIB_JANSSON}/include
   ${CMAKE_CURRENT_BINARY_DIR}/lib/cmetrics
   ${CMAKE_CURRENT_BINARY_DIR}/include
 
   ${CMAKE_CURRENT_BINARY_DIR}/lib/monkey/include/
   ${CMAKE_CURRENT_BINARY_DIR}/lib/monkey/include/monkey/
+)
+
+if(NOT CARES_FOUND)
+  include_directories(
+    ${FLB_PATH_ROOT_SOURCE}/${FLB_PATH_LIB_CARES}/include
+    ${CMAKE_CURRENT_BINARY_DIR}/${FLB_PATH_LIB_CARES}
+  )
+endif()
 
-  ${CMAKE_CURRENT_BINARY_DIR}/lib/nghttp2
-  ${CMAKE_CURRENT_BINARY_DIR}/lib/nghttp2/lib/includes/
-  ${FLB_PATH_ROOT_SOURCE}/${FLB_PATH_LIB_NGHTTP2}/lib/includes/
+if(FLB_AVRO_ENCODER)
+  include_directories(
+    ${CMAKE_CURRENT_BINARY_DIR}/${FLB_PATH_LIB_JANSSON}/include
   )
+endif()
+
+if(FLB_LUAJIT AND (NOT LUAJIT_FOUND))
+  include_directories(
+    ${FLB_PATH_ROOT_SOURCE}/${FLB_PATH_LIB_LUAJIT}/src
+    ${CMAKE_CURRENT_BINARY_DIR}/lib/luajit-cmake
+  )
+endif()
+
+if(NOT NGHTTP2_FOUND)
+  include_directories(
+    ${CMAKE_CURRENT_BINARY_DIR}/lib/nghttp2
+    ${CMAKE_CURRENT_BINARY_DIR}/lib/nghttp2/lib/includes
+    ${FLB_PATH_ROOT_SOURCE}/${FLB_PATH_LIB_NGHTTP2}/lib/includes
+  )
+endif()
 
 if(FLB_IN_KAFKA OR FLB_OUT_KAFKA)
     include_directories(${FLB_PATH_ROOT_SOURCE}/${FLB_PATH_LIB_RDKAFKA}/src/)