diff -urN cmake-3.6.1/Modules/Compiler/GNU.cmake cmake-3.6.1-patched/Modules/Compiler/GNU.cmake
--- cmake-3.6.1/Modules/Compiler/GNU.cmake	2016-07-22 23:50:22.000000000 +1000
+++ cmake-3.6.1-patched/Modules/Compiler/GNU.cmake	2016-08-26 17:43:28.468035438 +1000
@@ -46,10 +46,10 @@
 
   # Initial configuration flags.
   set(CMAKE_${lang}_FLAGS_INIT "")
-  set(CMAKE_${lang}_FLAGS_DEBUG_INIT "-g")
+  set(CMAKE_${lang}_FLAGS_DEBUG_INIT "")
   set(CMAKE_${lang}_FLAGS_MINSIZEREL_INIT "-Os -DNDEBUG")
-  set(CMAKE_${lang}_FLAGS_RELEASE_INIT "-O3 -DNDEBUG")
-  set(CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT "-O2 -g -DNDEBUG")
+  set(CMAKE_${lang}_FLAGS_RELEASE_INIT "-DNDEBUG")
+  set(CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT "-DNDEBUG")
   set(CMAKE_${lang}_CREATE_PREPROCESSED_SOURCE "<CMAKE_${lang}_COMPILER> <DEFINES> <INCLUDES> <FLAGS> -E <SOURCE> > <PREPROCESSED_SOURCE>")
   set(CMAKE_${lang}_CREATE_ASSEMBLY_SOURCE "<CMAKE_${lang}_COMPILER> <DEFINES> <INCLUDES> <FLAGS> -S <SOURCE> -o <ASSEMBLY_SOURCE>")
   if(NOT APPLE OR NOT CMAKE_${lang}_COMPILER_VERSION VERSION_LESS 4) # work around #4462
diff -urN cmake-3.6.1/Modules/Compiler/GNU-Fortran.cmake cmake-3.6.1-patched/Modules/Compiler/GNU-Fortran.cmake
--- cmake-3.6.1/Modules/Compiler/GNU-Fortran.cmake	2016-07-22 23:50:22.000000000 +1000
+++ cmake-3.6.1-patched/Modules/Compiler/GNU-Fortran.cmake	2016-08-26 17:43:28.468035438 +1000
@@ -6,7 +6,7 @@
 
 # No -DNDEBUG for Fortran.
 set(CMAKE_Fortran_FLAGS_MINSIZEREL_INIT "-Os")
-set(CMAKE_Fortran_FLAGS_RELEASE_INIT "-O3")
+set(CMAKE_Fortran_FLAGS_RELEASE_INIT "")
 
 # No -isystem for Fortran because it will not find .mod files.
 unset(CMAKE_INCLUDE_SYSTEM_FLAG_Fortran)