In commit 0e96a204 (MSVC: Add abstraction for debug information
format, 2022-08-25, v3.25.0-rc1~142^2~1) we overlooked populating the
runtime library selection flags for the Microsoft assembler.  Its
compiler id is `MSVC`, so our generators expect the table to be
populated.  It only supports `Embedded` debug info.  Use empty flags for
the other formats.

Without this fix, enabling the `ASM_MASM` language with policy `CMP0141`
set to `NEW` causes an error due to the missing table entries.

Fixes: #24249