update the comments

crt/CMakeLists.txt

@@ -43,9 +43,10 @@ if(UNIX AND NOT APPLE)
         string(TOLOWER "${CMAKE_SYSTEM_PROCESSOR}" CMAKE_SYSTEM_PROCESSOR_LOWER)
         if(CMAKE_SYSTEM_PROCESSOR_LOWER MATCHES "x86_64|amd64|x86|i386|i686" AND CMAKE_SIZEOF_VOID_P EQUAL 4)
             # Add -msse2 for x86-32bit because of https://github.com/aws/aws-lc/commit/6fe8dcbe96e580ea85233fdb98a142e42951b70b
-            # In some cases such as when building in Docker, where the host-level architecture is 64-bit
-            # but the Docker image should result in building for a 32-bit architecture. So that when ARCH
-            # is originally detected as 64-bit, perform an additional check to determine whether to build as 32-bit or 64-bit.
+            # Be wary that CMAKE_SYSTEM_PROCESSOR may not correspond to the target architecture when cross-compiling.
+            # (E.g. on Windows, the host may be AMD64 even when using a MSVC cl compiler with a 32-bit target).
+            # The CMAKE_TOOLCHAIN_FILE is supposed to set it correctly, but may not have.
+            # So, check for both CMAKE_SIZEOF_VOID_P and CMAKE_SYSTEM_PROCESSOR_LOWER for x86-32bit
             set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -msse2")
         endif()