Correct LTO RAM usage in compiling instructions (#4710)

development/compiling/compiling_for_windows.rst

@@ -141,7 +141,7 @@ dependencies. Running it will bring up the Project Manager.
           If you are compiling Godot with MinGW, you can make the binary
           even smaller and faster by adding the SCons option ``use_lto=yes``.
           As link-time optimization is a memory-intensive process,
-          this will require about 3 GB of available RAM while compiling.
+          this will require about 7 GB of available RAM while compiling.
 
 .. note:: If you want to use separate editor settings for your own Godot builds
           and official releases, you can enable

development/compiling/compiling_for_x11.rst

@@ -127,7 +127,7 @@ manager.
           If you are compiling Godot with GCC, you can make the binary
           even smaller and faster by adding the SCons option ``use_lto=yes``.
           As link-time optimization is a memory-intensive process,
-          this will require about 3 GB of available RAM while compiling.
+          this will require about 7 GB of available RAM while compiling.
 
 .. note:: If you want to use separate editor settings for your own Godot builds
           and official releases, you can enable

development/compiling/optimizing_for_size.rst

@@ -140,7 +140,7 @@ and MSVC compilers:
 
     scons p=windows target=release tools=no use_lto=yes
 
-Linking becomes much slower with this option, so it should be used only for
+Linking becomes much slower and more RAM consuming with this option, so it should be used only for
 release builds.
 
 Stripping binaries