[CMAKE] Enable C4101 (unreferenced local variable) for MSVC builds.

This is already an error in GCC builds, so will make it harder for the
MSVC crowd to accidentally break GCC build.

Author: ThFabba

sdk/cmake/msvc.cmake

@@ -95,6 +95,7 @@ add_compile_flags("/wd4018")
 # - TODO: C4090: different 'modifier' qualifiers (for C programs only;
 #          for C++ programs, the compiler error C2440 is issued)
 # - C4098: void function returning a value
+# - C4101: unreferenced local variable
 # - C4113: parameter lists differ
 # - C4129: unrecognized escape sequence
 # - C4133: incompatible types - from '<x> *' to '<y> *'
@@ -108,7 +109,7 @@ add_compile_flags("/wd4018")
 # - C4700: uninitialized variable usage
 # - C4715: 'function': not all control paths return a value
 # - C4716: function must return a value
-add_compile_flags("/we4013 /we4020 /we4022 /we4028 /we4047 /we4098 /we4113 /we4129 /we4133 /we4163 /we4229 /we4311 /we4312 /we4313 /we4477 /we4603 /we4700 /we4715 /we4716")
+add_compile_flags("/we4013 /we4020 /we4022 /we4028 /we4047 /we4098 /we4101 /we4113 /we4129 /we4133 /we4163 /we4229 /we4311 /we4312 /we4313 /we4477 /we4603 /we4700 /we4715 /we4716")
 
 # - C4189: local variable initialized but not referenced
 # Not in Release mode and not with MSVC 2010