ENH: add a variable for CMAKE_COMPILER_IS_GNUCXX

Templates/CMakeSystemConfig.cmake.in

@@ -50,3 +50,4 @@ SET (CMAKE_X_CFLAGS           "@X_CFLAGS@" CACHE STRING "X11 extra flags")
 SET (CMAKE_HAS_X              @CMAKE_HAS_X@ CACHE INTERNAL "Is X11 around")
 SET (CMAKE_NO_ANSI_STREAM_HEADERS @CMAKE_NO_ANSI_STREAM_HEADERS@ CACHE INTERNAL "does the compiler support headers like iostream ")
 SET (CMAKE_NO_STD_NAMESPACE       @CMAKE_NO_STD_NAMESPACE@  CACHE INTERNAL "does the compiler support std:: ")
+SET (CMAKE_COMPILER_IS_GNUCXX     @CMAKE_COMPILER_IS_GNUCXX@ CACHE INTERNAL "Is the compile GNU C++")

Templates/configure

@@ -3062,6 +3062,11 @@ esac
 
 
 
+CMAKE_COMPILER_IS_GNUGXX=0
+if test $ac_cv_prog_gxx = yes; then
+	CMAKE_COMPILER_IS_GNUCXX=1
+fi
+
 # generate output files.
 # create mkdir files just to make some of the directories
 
@@ -3248,6 +3253,7 @@ s%@RUNMAKE@%$RUNMAKE%g
 s%@CMAKE_AR_TMP@%$CMAKE_AR_TMP%g
 s%@CMAKE_AR@%$CMAKE_AR%g
 s%@CMAKE_AR_ARGS@%$CMAKE_AR_ARGS%g
+s%@CMAKE_COMPILER_IS_GNUCXX@%$CMAKE_COMPILER_IS_GNUCXX%g
 
 CEOF
 EOF

Templates/configure.in

@@ -559,6 +559,11 @@ esac
 AC_SUBST(CMAKE_AR)
 AC_SUBST(CMAKE_AR_ARGS)
 
+CMAKE_COMPILER_IS_GNUGXX=0
+if test $ac_cv_prog_gxx = yes; then
+	CMAKE_COMPILER_IS_GNUCXX=1
+fi
+AC_SUBST(CMAKE_COMPILER_IS_GNUCXX)
 # generate output files.
 # create mkdir files just to make some of the directories