Revert commit 1a8712d31a (cmGeneratorTarget: always provide a compile
PDB filename, 2025-11-24). It changed our long-standing conditions for
when a naming a compiler-generated `.pdb` file is explicitly named.
It also caused some `BuildDepends` and `RunCMake.BuildDepends` failures
in VS builds that went unnoticed before merging.
Issue: #27401
As of commit f78f592b78 (pchreuse: defer target existence enforcement to
generation time, 2025-06-16) via !10887, the compile PDB directory is
always set. Some codepaths used the total computation as a signal to
build the path themselves. But the filename was not specified, so the
resulting filename ended up changing. Always create the filename as
expected.
Fixes: #27401
In commit 26bf32cdc6 (LLVMFlang: Add support for targeting MSVC ABI on
Windows, 2023-09-28, v3.28.0-rc1~10^2) we incorrectly recorded `-g` as
supporting the `ProgramDatabase` format, but it is actually `Embedded`,
matching Clang.
In order to support easy integration with C and C++ projects that use
the `.pdb` debug formats, pretend LLVMFlang supports them and just don't
actually emit any debug information.
Issue: #24840
Brad King