Fixed gcc version parsing.

cmake/OpenCVDetectCXXCompiler.cmake

@@ -55,7 +55,10 @@ if(CMAKE_COMPILER_IS_GNUCXX)
 
     # Typical output in CMAKE_OPENCV_GCC_VERSION_FULL: "c+//0 (whatever) 4.2.3 (...)"
     # Look for the version number
-    string(REGEX MATCH "[0-9]+.[0-9]+(.[0-9]+)?" CMAKE_GCC_REGEX_VERSION "${CMAKE_OPENCV_GCC_VERSION_FULL}")
+    string(REGEX MATCH "[0-9]+.[0-9]+.[0-9]+" CMAKE_GCC_REGEX_VERSION "${CMAKE_OPENCV_GCC_VERSION_FULL}")
+    if(NOT CMAKE_GCC_REGEX_VERSION)
+      string(REGEX MATCH "[0-9]+.[0-9]+" CMAKE_GCC_REGEX_VERSION "${CMAKE_OPENCV_GCC_VERSION_FULL}")
+    endif()
 
     # Split the three parts:
     string(REGEX MATCHALL "[0-9]+" CMAKE_OPENCV_GCC_VERSIONS "${CMAKE_GCC_REGEX_VERSION}")