Merge pull request opencv#26234 from zachlowry:apply-gcc6-fix-on-each-directory

Move the gcc6 compatibility check to occur on a per-directory basis, … opencv#26234

Proposed fix for opencv#26233 opencv#26233

### Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch
- [x] There is a reference to the original bug report and related work
- [ ] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [ ] The feature is well documented and sample code can be built with the project CMake

Author: zachlowry

cmake/OpenCVUtils.cmake

@@ -353,23 +353,23 @@ function(ocv_target_include_directories target)
   #ocv_debug_message("ocv_target_include_directories(${target} ${ARGN})")
   _ocv_fix_target(target)
   set(__params "")
-  if(CV_GCC AND NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS "6.0" AND
-      ";${ARGN};" MATCHES "/usr/include;")
-    return() # workaround for GCC 6.x bug
-  endif()
-  set(__params "")
   set(__system_params "")
   set(__var_name __params)
   foreach(dir ${ARGN})
     if("${dir}" STREQUAL "SYSTEM")
       set(__var_name __system_params)
     else()
-      get_filename_component(__abs_dir "${dir}" ABSOLUTE)
-      ocv_is_opencv_directory(__is_opencv_dir "${dir}")
-      if(__is_opencv_dir)
-        list(APPEND ${__var_name} "${__abs_dir}")
+      if(CV_GCC AND NOT CMAKE_CXX_COMPILER_VERSION VERSION_LESS "6.0" AND
+          dir MATCHES "/usr/include$")
+         # workaround for GCC 6.x bug
       else()
-        list(APPEND ${__var_name} "${dir}")
+        get_filename_component(__abs_dir "${dir}" ABSOLUTE)
+        ocv_is_opencv_directory(__is_opencv_dir "${dir}")
+        if(__is_opencv_dir)
+          list(APPEND ${__var_name} "${__abs_dir}")
+        else()
+          list(APPEND ${__var_name} "${dir}")
+        endif()
       endif()
     endif()
   endforeach()