Fixed precompiled headers build on Linux

cmake/OpenCVPCHSupport.cmake

@@ -24,10 +24,12 @@ IF(CMAKE_COMPILER_IS_GNUCXX)
     ENDIF()
 
     SET(_PCH_include_prefix "-I")
+    SET(_PCH_isystem_prefix "-isystem")
 
 ELSEIF(WIN32)
     SET(PCHSupport_FOUND TRUE) # for experimental msvc support
     SET(_PCH_include_prefix "/I")
+    SET(_PCH_isystem_prefix "/I")
 ELSE()
     SET(PCHSupport_FOUND FALSE)
 ENDIF()
@@ -50,7 +52,11 @@ MACRO(_PCH_GET_COMPILE_FLAGS _out_compile_flags)
 
     GET_DIRECTORY_PROPERTY(DIRINC INCLUDE_DIRECTORIES )
     FOREACH(item ${DIRINC})
+        if(item MATCHES "^${OpenCV_SOURCE_DIR}/modules/")
           LIST(APPEND ${_out_compile_flags} "${_PCH_include_prefix}\"${item}\"")
+        else()
+          LIST(APPEND ${_out_compile_flags} "${_PCH_isystem_prefix}\"${item}\"")
+        endif()
     ENDFOREACH(item)
 
     GET_DIRECTORY_PROPERTY(_directory_flags DEFINITIONS)

modules/ts/include/opencv2/ts/ts.hpp

@@ -41,9 +41,6 @@
 #ifndef GTEST_USES_POSIX_RE
 #  define GTEST_USES_POSIX_RE 0
 #endif
-// #ifdef __GNUC__
-// #  pragma GCC diagnostic ignored "-Wmissing-declarations"
-// #endif
 
 #include "opencv2/core/core.hpp"