Removed -static-libgcc linker flag that caused Pcbnew to crash on Windows when...

Removed -static-libgcc linker flag that caused Pcbnew to crash on Windows when raising an exception in release builds using MinGW GCC 4.6.1

CMakeLists.txt

@@ -78,7 +78,7 @@ if(CMAKE_COMPILER_IS_GNUCXX)
     # Set default flags for Release build.
     set(CMAKE_C_FLAGS_RELEASE "-Wall -O2 -DNDEBUG ")
     set(CMAKE_CXX_FLAGS_RELEASE "-Wall -O2 -DNDEBUG")
-    set(CMAKE_EXE_LINKER_FLAGS_RELEASE "-s -static-libgcc")
+    set(CMAKE_EXE_LINKER_FLAGS_RELEASE "-s")
 
     # Set default flags for Debug build.
     set(CMAKE_C_FLAGS_DEBUG "-Wall -g3 -ggdb3 -DDEBUG")