PCH: disable by default on all platforms except MSVC

CMakeLists.txt

@@ -475,7 +475,7 @@ OCV_OPTION(INSTALL_TESTS            "Install accuracy and performance test binar
 # OpenCV build options
 # ===================================================
 OCV_OPTION(ENABLE_CCACHE              "Use ccache"                                               (UNIX AND NOT IOS AND (CMAKE_GENERATOR MATCHES "Makefile" OR CMAKE_GENERATOR MATCHES "Ninja")) )
-OCV_OPTION(ENABLE_PRECOMPILED_HEADERS "Use precompiled headers"                                  ON IF (MSVC OR (NOT IOS AND NOT CMAKE_CROSSCOMPILING) ) )
+OCV_OPTION(ENABLE_PRECOMPILED_HEADERS "Use precompiled headers"                                  MSVC IF (MSVC OR (NOT IOS AND NOT CMAKE_CROSSCOMPILING) ) )
 OCV_OPTION(ENABLE_SOLUTION_FOLDERS    "Solution folder in Visual Studio or in other IDEs"        (MSVC_IDE OR CMAKE_GENERATOR MATCHES Xcode) )
 OCV_OPTION(ENABLE_PROFILING           "Enable profiling in the GCC compiler (Add flags: -g -pg)" OFF  IF CV_GCC )
 OCV_OPTION(ENABLE_COVERAGE            "Enable coverage collection with  GCov"                    OFF  IF CV_GCC )