Fix binary size regression with MSVC

Reduce sel_ldr.exe from 3.0M to 1.6M by changing linker flags. The old
Google release is 1.5M.

This commit was generated via LLM. I verified that /DEBUG really is
passed in the linker command line for some reason, as per its comment.

Author: slipher

site_scons/site_tools/target_platform_windows.py

@@ -402,7 +402,10 @@ def RES(*argv, **karg):
       ],
       # Omit the absolute pathname of the .pdb debugging info file
       # from the executable, and just use a relative pathname.
-      LINKFLAGS_OPTIMIZED=['/PDBALTPATH:%_PDB%'],
+      # SCons passes /DEBUG when PDB is set, which defaults to incremental
+      # linking without dead-code removal, so override that explicitly.
+      LINKFLAGS_OPTIMIZED=['/PDBALTPATH:%_PDB%', '/INCREMENTAL:NO', '/OPT:REF',
+                           '/OPT:ICF'],
 
       # Settings for component_builders
       COMPONENT_LIBRARY_LINK_SUFFIXES=['.lib'],