Add detection of gcc versions that do not support isysroot option and do not use it for them.

Modules/Platform/Darwin.cmake

@@ -182,6 +182,20 @@ IF(XCODE)
   SET(CMAKE_INCLUDE_SYSTEM_FLAG_CXX)
 ENDIF(XCODE)
 
+IF(NOT CMAKE_OSX_GCC_SUPPORT_ISYSROOT)
+  IF("${CMAKE_C_COMPILER_ID}" MATCHES "GNU")
+    EXECUTE_PROCESS(COMMAND ${CMAKE_C_COMPILER} "--version"
+      OUTPUT_VARIABLE GCC_VERSION)
+  ENDIF("${CMAKE_C_COMPILER_ID}" MATCHES "GNU")
+  STRING(REGEX REPLACE "^[^ ]+[ ][^ ]+[ ]([^ ]+).*$" "\\1"
+         gcc_version_tmp "${GCC_VERSION}")
+  IF(${gcc_version_tmp} VERSION_GREATER 3.9)
+    SET(CMAKE_OSX_GCC_SUPPORT_ISYSROOT TRUE CACHE INTERNAL "GCC supports isysroot")
+  ELSE(${gcc_version_tmp} VERSION_GREATER 3.9)
+    SET(CMAKE_OSX_GCC_SUPPORT_ISYSROOT FALSE CACHE INTERNAL "GCC supports isysroot")
+  ENDIF(${gcc_version_tmp} VERSION_GREATER 3.9)
+ENDIF(NOT CMAKE_OSX_GCC_SUPPORT_ISYSROOT)
+
 # Need to list dependent shared libraries on link line.  When building
 # with -isysroot (for universal binaries), the linker always looks for
 # dependent libraries under the sysroot.  Listing them on the link

Source/cmLocalGenerator.cxx

@@ -1759,9 +1759,14 @@ void cmLocalGenerator::AddLanguageFlags(std::string& flags,
       this->Makefile->GetDefinition("CMAKE_OSX_SYSROOT_DEFAULT");
     const char* deploymentTarget = 
       this->Makefile->GetDefinition("CMAKE_OSX_DEPLOYMENT_TARGET");
-
+    const char* gccHasIsysroot = 
+      this->Makefile->GetRequiredDefinition("CMAKE_OSX_GCC_SUPPORT_ISYSROOT");
+    bool hasIsysroot = true;
+    if(cmSystemTools::IsOff(gccHasIsysroot))
+      {
+      hasIsysroot = false;
+      }
     bool flagsUsed = false;
-
     if(osxArch && sysroot && lang && (lang[0] =='C' || lang[0] == 'F'))
       {
       std::vector<std::string> archs;
@@ -1787,16 +1792,17 @@ void cmLocalGenerator::AddLanguageFlags(std::string& flags,
           flags += " -arch ";
           flags += *i;
           }
-
-        flags += " -isysroot ";
-        flags += sysroot;
-
+        if(hasIsysroot)
+          {
+          flags += " -isysroot ";
+          flags += sysroot;
+          }
         flagsUsed = true;
         }
       }
 
     if(!flagsUsed && sysroot && sysrootDefault &&
-       strcmp(sysroot, sysrootDefault) != 0)
+       strcmp(sysroot, sysrootDefault) != 0 && hasIsysroot)
       {
       flags += " -isysroot ";
       flags += sysroot;